Northwest

Climate Change Impacts

Idaho Ÿ• Oregon •Ÿ Washington

The following is a compilation of climate change impacts occurring right here, right now in the Northwest, as well as projected impacts, economic and human health consequences, and notable recent events. The Northwest is home to 12 million inhabitants. Climate change already poses a challenge to the Northwest, from extreme heat to wildfires, and conditions are likely to increase in severity.


Water Cycle 

Right Here, Right Now

Projected Trends

  • The largest hydrologic responses to climate change are expected to occur in basins with significant snow accumulation, where warming increases winter flows and advances the timing of spring melt.
  • By 2050, snowmelt is projected to shift three to four weeks earlier than the 20th century average, and summer flows are projected to be substantially lower, even for an emissions scenario that assumes substantial emissions reductions (B1).
  • Modeling studies indicate, with near 100% likelihood and for all emissions scenarios, that reductions in summer flow will occur by 2050 in basins with significant snowmelt.
  • Changes in river-related flood risk depends on many factors, but warming is projected to increase flood risk the most in basins with both winter rainfall and late spring snowmelt-related runoff peaks and remain largely unchanged in snow-dominant basins.
  • Averaged over the region, the number of days with more than one inch of precipitation is projected to increase 13% in 2041 to 2070 compared with 1971 to 2000 under a scenario that assumes a continuation of current rising emissions trends. 
  • The risk of a water-short year – when Yakima basin junior water rights holders are allowed only 75% of their water right amount – is projected to increase from 14% in the late 20th century to 32% by 2020 and 77% by 2080, assuming no adaptation and under the A1B scenario.

Economic Impacts

Impacts to Human Health and Wellbeing

  • Regional power planners have expressed concerns over the existing hydroelectric system’s potential inability to provide adequate summer electricity given the combination of climate change, demand growth, and operating constraints. Vulnerability to projected changes in snowmelt timing is probably highest in basins with the largest hydrologic response to warming and lowest management flexibility – that is, fully allocated, mid-elevation, temperature-sensitive, mixed rain-snow watersheds with existing conflicts among users of summer water (e.g. the Yakima River basin). 

 


Forests and Wildfires

Right Here, Right Now

  • Warmer and drier conditions have helped increase the number and extent of wildfires in western U.S. forests since the 1970s.
  • 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.
  • Higher temperatures and drought stress are contributing to outbreaks of mountain pine beetles that are increasing pine mortality in drier Northwest forests.

Projected Trends

  • By the 2080s, the median annual area burned in the Northwest would quadruple relative to the 1916 to 2007 period to 2 million acres (range of 0.2 to 9.8 million acres) under the A1B scenario. Averaged over the region, this would increase the probability that 2.2 million acres would burn in a year from 5% to nearly 50%.
  • Northwest summers are already dry and models project that, by the end of the century, the region will likely experience a 10% reduction in summer precipitation (the average projected change) and as much as a 30% reduction (the high end estimate). Unusually dry summers have many noticeable consequences including greater extent of wildfires throughout the region.
  • One study investigating wildfire activity in the western U.S. finds that if temperatures rise 3.2°F by mid-century, this could lead to a 54% increase in the annual area burned. The same study finds that among western forests, the Pacific Northwest and Rocky Mountains will likely experience the greatest increases in annual burn area with a 78% and 175% increase.
  • The cumulative effects of disturbance – and possibly interactions between insects and fires – will cause the greatest changes in Northwest forests.
  • Under higher emissions scenarios, extensive conversion of subalpine forests to other forest types is projected by the 2080s.
  • Between now and the end of this century, the elevation of suitable beetle habitat is projected to increase as temperature increases, exposing higher-elevation forests to the pine beetle, but ultimately limiting available area as temperatures exceed the beetles’ optimal temperatures. As a result, the proportion of Northwest pine forests where mountain pine beetles are most likely to survive is projected to first increase (27% higher in 2001 to 2030 compared to 1961 to 1990) and then decrease (about 49% to 58% lower by 2071 to 2100).

Economic Impacts

Impacts to Human Health and Wellbeing

Recent Events

  • Since the beginning of the 2014 wildfire season in Washington up until the end of August, the Department of Natural Resources said wildfires have burned 363,000 acres, or 550 square miles of land, destroying homes along the way. That’s about 6 times worse than the average amount of acres burned per year in Washington, state forest officials said. Fighting the fires has been costly, too — the state says it spent $81 million this year, even though its annual budget is only $25 million.
  • The 2013 fire season in Oregon was severe, both in terms of loss and damage. Costs set a record, and more than 100,000 state-protected areas burned, the most since 1951.

 


Extreme Heat

Right Here, Right Now

Projected Trends

Economic Impacts

  • Warming, coupled with reduction in summer flows in snow-fed rivers, could increase agricultural and other demands, potentially producing irrigation water shortages.
  • Projected increases in average temperature and hot weather episodes and decreases in summer soil moisture would reduce yields of spring and winter wheat in rain-fed production zones of Washington State by the end of this century by as much as 25% relative to 1975 to 2005.
  • Because tree fruit requires chilling to ensure uniform flowering and fruit set and wine grape varieties have specific chilling requirements for maturation, warming could adversely affect currently grown varieties of these commodities. Most published projections of climate change impacts on Northwest agriculture are limited to Washington State and have focused on major commodities, although more than 300 crops are grown in the region

Impacts to Human Health and Wellbeing

  • Projected warming in Washington would likely result in 101 additional deaths among persons aged 45 and above during heat events in 2025 and 156 additional deaths in 2045 in the greater Seattle are alone (relative to 1980-2006). By mid-century, King County will likely experience 132 additional deaths between May and September annually due to worsened air quality caused by climate change.

Recent Events

  • In 2009, a heat wave scorched the Pacific Northwest, breaking records when temperatures topped 100°F (38°C).
  • During the summer of 2014, four Oregon cities—Salem, Bend, Klamath Falls and Medford—broke records with the highest July on record, with devastating impacts on drought and fire.
  • During the summer of 2010 in Washington, five counties saw record-breaking temperatures.

 


Coasts and Sea Level Rise

Right Here, Right Now

  • Much of the Northwest coastline is rising due to a geophysical force known as “tectonic uplift,” which raises the land surface. Because of this, apparent sea level rise is less than the currently observed global average. However, a major earthquake along the Cascadia subduction zone, expected within the next few hundred years, would immediately reverse centuries of uplift and, based on historical evidence, increase relative sea level 40 inches or more.
  • Northwest coastal waters are among the most acidified worldwide, especially in spring and summer with coastal upwelling combined with local factors in estuaries.

Projected Trends

  • For the Washington, Oregon, and California coasts north of Cape Mendocino, sea level is projected to rise 24 inches over the next century. Sea level rise in this region is projected to be lower than the global average because tectonic plate movement is causing the land to rise at about 3/5 to 11/5 inches per decade.
  • An earthquake magnitude 8 or greater along the Cascadia Subduction Zone would suddenly raise sea level along parts of the coast by an additional 3-7 feet over projected levels.
  • Research shows that if we stay on our current path, sea level at Seattle will likely rise by 0.6 to 1.0 foot between 2000 and 2050 and by 1.6 to 3.0 feet between 2000 and 2100. Looking out to the tail risks, there is a 1-in-100 chance of more than 5.9 feet of sea level rise by 2100 in Seattle.
  • Some global climate models predict that the North Pacific storm track will shift northward as global climate warms during the next several decades, which would generate extreme wave heights and storm surges along the Oregon and Washington coasts.
  • All climate models project ample winter storm activity in the North Pacific in future decades, suggesting that periods of anomalously high sea level and high waves will continue to occur along the west coast.
  • Rising sea levels and increasing wave heights will exacerbate coastal erosion and shoreline retreat along the west coast. Projections using only historic rates of cliff erosion predict 10 to 30 meters or more of retreat along the west coast by 2100. An increase in the rate of sea-level rise combined with larger waves could significantly increase these rates.

Economic Impacts

  • The economy of the Northwest is dependent on its coastlines and is at risk due to threats—like acidification, coastal erosion, shoreline retreat, and sea level rise—that are connected to climate change.
  • A recent paper exploring the ecological impacts of acidification and other aspects of climate change found that acidification in isolation causes small reductions in the catch of fished species in five northeast Pacific food webs. However, when accounting for other climate change impacts (changes in primary production, species range, zooplankton community size structure, and ocean deoxygenation), acidification reduced fisheries landings by 20%relative to harvest under unchanged environmental conditions.

Impacts to Human Health and Wellbeing

Recent Events

  • Much of the damage along the Washington and Oregon coasts is caused by storms — particularly from the combined effects of large waves, storm surges, and high tides during a strong El Niño. Both Washington andOregon been declared a disaster area 5 times since 2000 and Oregon, due to severe storms and flooding.