- USGCRP Coordinators:
- Natalie Bennett, Adaptation and Assessment Analyst
- Christopher W. Avery, Senior Manager
- Susan Aragon-Long, Senior Scientist
<b>May</b>, C., C. Luce, J. Casola, M. Chang, J. Cuhaciyan, M. Dalton, S. Lowe, G. Morishima, P. Mote, A. Petersen, G. Roesch-McNally, and E. York, 2018: Northwest. In <i>Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment</i>, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 1036–1100. doi: 10.7930/NCA4.2018.CH24
Residents of the Northwest list the inherent qualities of the natural environment among the top reasons to live in the region. The Northwest is known for clean air, abundant water, low-cost hydroelectric power, vast forests, extensive farmlands, and an array of outdoor recreation that includes hiking, boating, fishing, hunting, and skiing. Warming and related changes in climate are already affecting aspects of the Northwest’s identity such as its natural resource economy and its cultural heritage that is deeply embedded within the natural environment. The built systems that support Northwest residents and the health of residents themselves are also already experiencing the effects of climate change. The communities on the front lines of climate change experience the first, and often the worst, effects. Frontline communities in the Northwest include tribes and Indigenous peoples, the economically disadvantaged, and those most dependent on natural resources for their livelihoods.
Detroit Lake Reservoir During Multiyear Drought
The region has warmed substantially—nearly 2°F since 1900—and this warming is partially attributable to human-caused emissions of greenhouse gases.2,3,4 Warmer winters have led to reductions in the mountain snowpack5,6 that historically blanketed the region’s mountains, increasing wildfire risk (Ch. 6: Forests, KM 1)7,8 and speeding the usually slow release of water for communities, agriculture, rivers, and soils. In 2015, record winter warmth led to record-low snowpack in much of the Northwest’s mountains as winter precipitation fell as rain instead of snow,9 resulting in drought, water scarcity, and large wildfires that negatively affected farmers, hydropower, drinking water, salmon, and recreation. In addition, warmer ocean temperatures led to shifts in the marine ecosystem, challenges for salmon, and a large harmful algal bloom.10 The extreme climate-related events of 2015 have prompted Northwest states, cities, tribes, and others to increase and prioritize climate preparedness efforts, as evidenced by the presentations at the 6th and 7th annual Northwest Climate Conference (http://pnwclimateconference.org/CdA2015/ and http://pnwclimateconference.org/Stevenson2016/).
Climate change affects the interrelationships between the environment and the people of the Northwest, and extreme climate events, such as those that occurred during 2015, provide a preview of what may be more commonplace under a warmer future climate (Figure 24.2). The Northwest is projected to continue to warm during all seasons under all future scenarios, although the rate of warming depends on current and future emissions.11 The warming trend is projected to be accentuated in certain mountain areas in late winter and spring,9 further exacerbating snowpack loss and increasing the risk for insect infestations and wildfires.12 In central Idaho and eastern Oregon and Washington, vast mountain areas have already been transformed by mountain pine beetle infestations, wildfires, or both, but the western Cascades and coastal mountain ranges have less experience with these growing threats.13
Figure 24.2: Climate Change Will Impact Key Aspects of Life in the Northwest
Average winter precipitation is expected to increase over the long term, but year-to-year variability in precipitation is also projected to increase.11 Years of abnormally low precipitation and extended drought conditions are expected to occur throughout the century,11 and extreme events, like heavy rainfall associated with atmospheric rivers, are also anticipated to occur more often.14 Along the coast, severe winter storms are also projected to occur more often, such as occurred in 2015 during one of the strongest El Niño events on record.15 El Niño winter storms contributed to storm surge, large waves, coastal erosion, and flooding in low-lying coastal areas (Ch. 8: Coastal, KM 1).16 Changes in the ocean environment, such as warmer waters, altered chemistry, sea level rise, and shifts in the marine ecosystems are also expected (Ch. 9: Oceans). These projected changes affect the Northwest’s natural resource economy, cultural heritage, built infrastructure, recreation, and the health and welfare of Northwest residents.
See Full Chapter & References