United States	AllOUSt 2016
Environmental Protection	y
Agency	EPA 430-F-16-039
What Climate Change
Oregon's climate is changing. Over the past century,
most of the state has warmed about two degrees (F).
Snowpack is melting earlier in the year, and the flow of
meltwater into streams during summer is declining. In
the coming decades, coastal waters will become more
acidic, streams will be warmer, wildfires may be more
common, and some rangelands may convert to desert.
Our climate is changing because the earth is warming.
People have increased the amount of carbon dioxide in
the air by 40 percent since the late 1700s. Other heat-
trapping greenhouse gases are also increasing. These
gases have warmed the surface and lower atmosphere
of our planet about one degree during the last 50 years.
Evaporation increases as the atmosphere warms,
which increases humidity, average rainfall, and the
frequency of heavy rainstorms in many places—but
contributes to drought in others.
Greenhouse gases are also changing the world's
oceans and ice cover. Carbon dioxide reacts with wa-
ter to form carbonic acid, so the oceans are becoming
more acidic. The surface of the ocean has warmed
about one degree during the last 80 years. Warming is
causing snow to melt earlier in spring, and mountain
glaciers are retreating. Even the great ice sheets on
Greenland and Antarctica are shrinking. Thus the sea
is rising at an increasing rate.
Marine and Coastal Ecosystems
Oregon's coastal waters are vulnerable to
acidification. The ocean here is more acidic
than most of the ocean, because nearby
currents bring relatively acidic water from the
deep ocean to the surface, especially during
spring and summer. Increasing acidity impairs
the ability of some types of shellfish to capture
minerals in the water to build their shells,
which can lead to thinner shells—or even
prevent shells from forming. At the Whiskey
Creek Hatchery in Netarts Bay, for example,
acidic seawater during spawning has reduced
the growth rates and survival of young
oysters. Acidity also thins the exoskeletons of
many species of plankton, which could reduce
the population of those plankton and the fish
that feed on them, and alter the entire marine food web. For example, young salmon eat
some of the types of shellfish and plankton that are vulnerable to acidification.
Rising ocean temperatures may also harm marine ecosystems. Warming waters can
increase the frequency of toxic algae blooms (such as "red tide") that cause shellfish
poisoning and lead to closures of beaches and shellfish beds. Warmer waters also allow
invasive species from southern waters to move northward.
Sea level rise will threaten coastal development and ecosystems. Erosion will threaten
homes and public property along the shore. Mudflats, marshes, and other tidal wetlands
provide habitat for birds and fish. As water levels rise, wetlands and beaches may be
submerged or squeezed between the rising sea and structures erected to protect coastal
Rising water temperatures, increasing
ocean acidity, and changes in the marine
ecosystem wili amplify observed losses
in commercially and recreationally
important fish stocks in the region in the
21st century. Credit: NOAA.
Pteropods, or "sea butterflies," are small free-swimming sea snails. They are an important source
of food for North Pacific Juvenile salmon, as well as whales and other marine species. The left
panel shows a shell collected from a live pteropod from a region where acidity is not yet very high.
The shell on the right is from a pteropod collected in a region where waters have acidified.
Credit: Nina Bednarsek, NOAA..
Rising temperatures in the last century. The warming in
Oregon has been similar to the average warming nationwide.
Source: EPA, Climate Change Indicators in the United States.
Temperature change (°F):

Snowpack, Streamflows, and Water Availability
The flows of water in rivers and streams are increasing during late winter
and early spring but decreasing during summer. Warmer winters have
reduced average snowpack in the Cascades by 20 percent since 1950.
The snowpack is now melting a few weeks earlier than during the
20th century, and, by 2050, it is likely to melt three to four weeks earlier.
Decreasing snowpack means there will be less water flowing through
streams during summer. Moreover, rising temperatures increase the rate
at which water evaporates (or transpires) into the air from soils and plants.
More evaporation means that less water will drain from the ground into
rivers and streams.
Declining snow and streamflow would harm some economic sectors and
aquatic ecosystems. Less snow means a shorter season for skiing and
other winter recreation. Water temperatures will rise, which would hurt
Chinook and sockeye salmon in the interior Columbia River Basin. The
combination of warmer water and lower flows would threaten salmon,
steelhead, and trout. Lower flows would also mean less hydroelectric

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Snowpack, 1955-2015 Percent Change
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