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 Climate
Impacts in the Northwest
Overview
The Northwest is best known for its vast Pacific coastline
and rainy weather. The region is home to the Cascade
Mountain Range that runs north-south through Washington and
Oregon, resulting in large climatic differences on the
western and eastern sides of the range. West of the
mountains, year-round temperatures are mild, winters are
wet, and summers are dry. East of the mountains, it is
typically sunnier and drier throughout the year, winters are
colder, and summers can be significantly hotter.
Over the last century, the average annual temperature in the
Northwest has risen by about 1.3°F. Temperatures are
projected to increase by approximately 3°F to 10°F by the
end of the century, with the largest increases expected in
the summer. Precipitation in the region has seen a decline
in both the amount of total snowfall and the proportion of
precipitation falling as snow. Declines in snowpack and
streamflows have been observed in the Cascades in recent
decades. In Washington state, record low snowpack values
were measured in April 2015 and in seventy-four percent of
long-term monitoring stations. Changes in average annual
precipitation in the Northwest are likely to vary over the
century. Summer precipitation is projected to decline by as
much as 30%, with less frequent but heavier downpours. |
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 Impacts
on Water Resources
A reliable supply of water is crucial for energy production,
agriculture, and ecosystems. Much of the Northwest's water
is stored naturally in winter snowpack in the mountains. The
snowpack melts and replenishes streams and rivers in the
late spring and summer, when there is very little rainfall.
Climate change threatens this natural storage by changing
the timing of snowmelt and the amount of water available in
streams and rivers (streamflow) throughout the year. Warmer
springs contribute to earlier melting of the snowpack,
higher streamflows in late winter and early spring, and
lower flows in summer. Spring snowmelt is projected to occur
three to four weeks earlier by mid-century and summer
streamflows are likely to decline. In the Cascade Mountains,
measurements of snowpack taken on April 1 (when snowpack is
usually at its peak) have decreased by about 20% since the
1950s.
Picture - Natural
surface water availability during late summer is projected
to decline across most of the Northwest. This map shows
expected changes in local runoff (shading) and streamflow
(colored circles) for the 2040s (compared to the period 1915
to 2006), assuming that heat-trapping greenhouse gases will
be reduced in the future. Source: USGCRP 2014
Climate change can also lead to changes in the type of
precipitation. Warmer winters cause more precipitation to
fall as rain instead of snow, particularly at lower
elevations. This reduces soil moisture, snow accumulation,
and the amount of water available from snowmelt. Further,
increased flood risks around rivers that receive waters from
both winter rains and peak runoff in late spring are
expected.
Changing streamflows are likely to strain water management
and worsen existing competition for water. Competing demands
for water currently include hydropower, agricultural
irrigation, municipal and industrial uses, and protection of
ecosystems and threatened or endangered species. Increasing
temperatures and populations could deepen demand and further
stress urban water supplies that are already at risk of
diminishing because of climate change.
Forty percent of the nation's hydropower is generated in the
Northwest. Lower streamflows will likely reduce
hydroelectric supply and could lead to large economic losses
in the region. Reduced streamflows combined with rising
temperatures and a growing population are raising concerns
about the ability to meet increased air conditioning and
other electricity demands.
For more information on climate change impacts, please visit
the Water Resources Impacts or the Energy Impacts pages. |
 Impacts
on Coastal Resources
Climate change is damaging the Northwest coastline.
Projections indicate an increase of 1 to 4 feet of global
sea level rise by the end of the century, which may have
implications for the 140,000 acres of the region that lie
within 3.3 feet of high tide. Sea level rise and storm surge
pose a risk to people, infrastructure, and ecosystems,
especially in low lying areas, which include Puget Sound.
Warming waters and ocean acidification threaten economically
important marine species and coastal ecosystems.
Picture - Many areas
of Seattle are projected to fall below sea level during high
tide by the end of the century. Shaded blue areas depict
three levels of sea level rise, assuming no adaptation. The
high (50 inches) and medium (13 inches) estimates are within
the range of current projections, while the highest level
(88 inches) includes the effect of storm surge. Source:
USGCRP 2014
Flooding, seawater inundation, and erosion are expected to
threaten coastal infrastructure, including properties,
highways, railways, wastewater treatment plants, stormwater
outfalls, and ferry terminals. Coastal wetlands, tidal
flats, and beaches are likely to erode or be lost as a
result of seawater inundation, which heightens the
vulnerability of coastal infrastructure to coastal storms.
Some coastal habitats may disappear if organisms are unable
to migrate inland because of topography or human
infrastructure. This is expected to affect shorebirds and
small forage fish, among other species. Warmer waters in
regional estuaries, including Puget Sound, may contribute to
an increase in harmful algal blooms, which could result in
beach closures and declines in recreational shellfish
harvests. Ocean acidification is also expected to negatively
impact important economic species, including oysters and
Pacific salmon.
For more information on climate change impacts on coastal
resources, please visit the Coastal Resources page. |
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 Impacts
on Ecosystems and Agriculture
Higher temperatures, changing streamflows, and increases in
pests and disease threaten forests, agriculture, and fish
populations in the Northwest.
Picture - Under
hotter, drier conditions, insects and fire can have large
cumulative impacts on forests. This is expected to be the
dominant driver of forest change in the near future. The top
map shows areas burned between 1984 and 2008 or affected by
insects or disease between 1997 and 2008. The bottom map
indicates the expected increase in area burned resulting
from a 2.2°F warming in average temperature. Source: USGCRP
2014
Forests make up nearly half of the Northwest landscape.
These areas provide important habitat for fish and wildlife
and support local economies, recreation, and traditional
tribal activities. Forests have become warmer and drier due
to rising temperatures, changes in precipitation, and
reduced soil moisture. These stresses make trees more
susceptible to insect outbreaks and disease and make forests
highly flammable. An increase in the number and size of
wildfires has been observed in the region in recent decades.
These impacts are expected to worsen in the future,
resulting in larger areas burned each year and expanded
spread of pests, including the mountain pine beetle. Some
types of forests and other ecosystems at high elevations are
also expected to disappear from the region by the end of the
century from inability to survive changing climatic
conditions. These changes are likely to have significant
effects on local timber revenues and bioenergy markets.
Commercial fish and shellfish harvested in the Northwest
were valued at $480 million in 2011. Warming waters have
already contributed to earlier migration of sockeye salmon
in some streams and earlier growth of algal blooms in some
lakes. Warmer waters are likely to increase spring and
summer disease and mortality in Chinook and sockeye salmon
in some river basins. Species that spend all or part of
their lives in rivers, including salmon, steelhead, and
trout, will suffer from decreased summer flows and increased
flooding and winter flows. Projections suggest that suitable
habitat for the four trout species in the region will
decline by an average of 47% near the end of this century,
compared to past decades.
Ocean acidification is also expected to negatively impact
shellfish, including oysters, and others species, including
Pacific salmon, resulting in economic and cultural
implications. Warmer coastal waters may alter migratory
patterns and areas of suitable habitat for marine species,
resulting in changes in abundances.
Agriculture is an important economic and cultural component
in rural areas of the Northwest. In the short-term, a longer
growing season and higher levels of atmospheric carbon
dioxide may be beneficial to crops. In the longer-term,
reduced water availability for irrigation, higher
temperatures, and changes in pests, diseases, and weeds may
harm crop yields.
For more information on climate change impacts on forests,
please visit the Forests Impacts page.
For more information on climate change impacts on
agriculture and food supply, please visit the Agriculture
and Food Supply Impacts page. |
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 Threatened
Salmon Populations
Human activities already threaten Northwest salmon
populations. These activities include dam building, logging,
pollution, and overfishing. Climate change impacts further
stress these salmon populations. Salmon are particularly
sensitive due to their seasonally timed migration upstream
to breed. Higher winter streamflows and earlier peak
steamflows due to climate change will damage spawning nests,
wash away incubating eggs, and force young salmon from
rivers prematurely. Lower summer streamflows and warmer
stream and ocean temperatures are less favorable for salmon
and other cold-water fish species. These climate change
impacts facilitate the spread of salmon diseases and
parasites. Many salmon species are already considered
threatened or endangered under the Federal Endangered
Species Act. Studies show that by 2100, one third of current
habitat for Northwest salmon and other coldwater fish will
be too warm for these species to tolerate.
Picture - Salmon
swimming upstream. Credit: US Fish and Wildlife Service |
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EPA Page |
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Key Points
Warming temperatures and declines in snowpack and streamflow
have been observed in the Northwest in recent decades.
Climate change will likely result in continued reductions in
snowpack and lower summer streamflows, worsening the
existing competition for water.
Higher temperatures, changing streamflows, and an increase
in pests, disease, and wildfire will threaten forests,
agriculture, and salmon populations.
Sea level rise is projected to increase erosion of
coastlines, escalating infrastructure and ecosystem risks. |
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Additional Climate Change Information |
Climate Change and Carbon Dioxide
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change
and carbon dioxide.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice. |
Carbon Dioxide and Climate Change
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of carbon dioxide
and climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice. |
Environmental Group Warns Earth's Health at Risk
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
A report by the World Wildlife Fund looked at thousands of animal populations
and found they have dropped significantly in 40 years. |
Sea Levels Rising at Fastest Rate in 3,000 years
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
A group of scientists say sea levels are rising at record rates. Another group
found that January temperatures in the Arctic reached a record high. |
Capturing CO2 Gas Is Not Easy
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
Most scientists agree that carbon-dioxide gas is partly to blame for climate
change: rising global temperatures. But capturing the CO2 gas released by power
stations is costly and difficult. |
Growth, Climate Change Threaten African Plants and
Animals
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
Researchers believe Africa may lose as much as 30 percent of its animal and
plant species by the end of this century. |
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