SEPA
United States
Environmental Protection
Agency
•tection
What Climate Change
Means for Oklahoma
August 2016
EPA 430-F-16-038

In the coming decades, Oklahoma will become
warmer, and both floods and droughts may be
more severe. Most of Oklahoma did not become
warmer during the last 50 to 100 years. But soils
have become drier, annual rainfall has increased,
and more rain arrives in heavy downpours. In
the coming decades, summers are likely to be
increasingly hot and dry, which would reduce the
productivity of farms and ranches, change parts of
the landscape, and possibly harm human health.
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.
While most of the earth warmed during the last
century, natural cycles and sulfates in the air
cooled eastern Oklahoma. Sulfates are air pol-
lutants that reflect sunlight back into space. Now
sulfate emissions are declining, and the factors that
once prevented parts of the state from warming
are unlikely to persist.
Temperature change (°F):
-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5
Changing temperatures in the last century. While most of the
nation has warned, eastern Oklahoma has cooled. Source:
EPA, Climate Change Indicators in the United States.
Precipitation and Water Resources
Changing the climate is likely to increase the demand for water but make it less
available. As rising temperatures increase evaporation and water use by plants,
soils are likely to become even drier. Average rainfall is likely to decrease during
spring and summer. Seventy years from now, the longest period without rain each
year is iikely to be at least three days longer than it is today. Increased evaporation
and decreased rainfall are likely to reduce the average flow of rivers and streams.
Drier soils will increase the need for farmers to irrigate their crops, but sufficient
water might not be available. Approximately 16 percent of Oklahoma's farmland
is irrigated. In the Panhandle, most irrigation water is ground water from the
High Plains Aquifer System. As a result, this aquifer is becoming depleted. Since
the 1950s, the amount of water stored in the aquifer has declined by more than
25 percent in parts of the Panhandle. (See map on back page.)
Decreased river flows can create problems for navigation, recreation, public water
supplies, and electric power generation. Commercial navigation can be suspended
during droughts when there is too little water to keep channels deep enough for
barge traffic. Decreased river flows can also lower the water level in lakes and
reservoirs, which may limit municipal water supplies; impair swimming, fishing,
and other recreational activities; and reduce hydroelectric power generation.
Conventional power plants also need adequate water for cooling. Compounding
the challenges for electric utilities, rising temperatures are expected to increase
the demand for electricity for air conditioning.
Agriculture
Increasing droughts and higher
temperatures are likely to interfere
with Oklahoma's farms and cattle
ranches. Hot weather causes cows
to eat less and grow more slowly,
and it can threaten their health.
Reduced water availability would
create challenges for ranchers, as
well as farmers who irrigate crops
such as wheat. Yields are likely to
decline by about 50 percent in fields
that can no longer be irrigated. The
early flowering of winter wheat could
have negative repercussions on
livestock farmers who depend on it
for feed.
A dry cornfield in Canadian County during the
2011 drought. Credit: Ron Hays, Oklahoma Farm
Report.

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/Wa:
OKLAHOMA
NEW MEXICO
<
TEXAS
Declines	No substantial change
More than 50%	10% to -10%
25% to 50%
10% to 25% Rises
¦ 10% to 25%
More than 25%
Area where the aquifer
stores little or no water
County boundary
Percent depletion of ground water in the High Plains Aquifer, 1950-2013.
Source: USGS.
Rainstorms and Tornadoes
Although summer droughts are likely to become more severe,
floods may also intensify. During the last 50 years, the amount of
rain falling during the wettest four days of the year has increased
about 15 percent in the Great Plains, Over the next several
decades, the amount of rainfall during the wettest days of the year
is likely to continue to increase, which would increase flooding.
Three days of heavy rain in May 2013 led to flooding in Hentyetta
(shown here) and other communities. Credit: Bruce Jones, The
Heniyettan.
Scientists do not know how the frequency and severity of
tornadoes will change. Rising concentrations of greenhouse gases
tend to increase humidity, and thus atmospheric instability, which
would encourage tornadoes. But wind shear is likely to decrease,
which would discourage tornadoes. Research is ongoing to learn
whether tornadoes will be more or less frequent in the future.
Because Oklahoma experiences about 60 tornadoes a year, such
research is closely followed by meteorologists in the state.
Hot Weather, Air Pollution, and Human Health
Hot days can be unhealthy—even dangerous. Seventy years from
now, Oklahoma is likely to have three to four times as many days
above 100°F as it has today. Certain people are especially
vulnerable, including children, the elderly, the sick, and the poor.
The elderly may be particularly prone to heat stress and other
heat-related health problems, including dehydration, cardio-
vascular strain, and lung problems. Those with low incomes may
also be vulnerable if they lack air conditioning.
Rising temperatures can also increase the formation of ground-
level ozone, a key component of smog. Ozone has a variety of
health effects, aggravates lung diseases such as asthma, and
increases the risk of premature death from heart or lung disease.
EPA and the Oklahoma Department of Environmental Quality have
been working to reduce ozone concentrations. As the climate
changes, continued progress toward clean air will become more
difficult.
Wildfires and Landscape Change
Higher temperatures and drought are likely to increase the sever-
ity, frequency, and extent of wildfires, which could harm property,
livelihoods, and human health. On average, more than 1 percent
of the land in Oklahoma has burned each decade since 1984.
Wildfire smoke pollutes the air and can increase medical visits for
chest pains, respiratory problems, and heart problems.
The combination of more fires and drier conditions may change
parts of Oklahoma's landscape. Many plants and animals living in
the dry lands of western Oklahoma are already near the limits of
what they can tolerate. In some cases, native vegetation may
persist as the climate changes. But when fire destroys the natural
cover, the native grasses and woody plants may be replaced by
non-native grasses, which can become established more readily
after a fire. Because non-native grasses are generally more prone
to intense fires, native plants may be unable to re-establish
themselves.
The sources of information about climate and the impacts of climate change in this publication are: the national climate assessments by the U.S. Global Change Research
Program, synthesis and assessment products by the U.S. Climate Change Science Program, assessment reports by the Intergovernmental Panel on Climate Change, and EPA's
Climate Change Indicators in the United States. Mention of a particular season, location, species, or any other aspect of an impact does not imply anything about the likelihood or
importance of aspects that are not mentioned. For more information about climate change science, impacts, responses, and what you can do, visit EPA's Climate Change website
at vmw.eDa.aov/climatechanae.

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