United States	AliOUSt 2016
Environmental Protection
Agency	EPA 430-F-16-043
United States
Environmental Protection
% W 1	Agency
What Climate Change
Means/frgouth Dakota
South Dakota's climate is changing. In the past century,
most of the state has warmed by one to two degrees (F).
Rainstorms are becoming more intense, and annual rainfall
is increasing. In the coming decades, summers are likely
to become increasingly hot, which may amplify some risks
to human health and decrease yields of some crops while
lengthening the growing season for others.
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 water 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, and sea level is rising, at an
increasing rate. Warming is causing snow to melt earlier in
Temperature change (°F):
¦1 -0.5 0 0 5 1 1.5 2 2.5 3 B.5
Rising temperatures in the last century. The waiming in South
Dakota has been more than the average waiming nationwide.
Source: EPA, Climate Change Indicators in the United States.
Precipitation and Water Resources
Changing climate is likely to increase the demand for water and
make it more available. Rising temperatures increase evapo-
ration and water use by plants, which make soils drier. But
rainfall is likely to increase enough to allow soil moisture to
increase slightly or remain about the same as today. More water
is likely to run off into the Missouri River and its tributaries.
The resulting increase in river flows could benefit recreational
boating, public water supplies, and electric power generation.
During droughts, decreased river flows can lower the water level
in lakes and reservoirs, which may limit municipal water supplies
and impair swimming, fishing, and other recreational activities.
But if more water flows through the rivers before or during a
drought, these problems will be less likely. Higher water flows
also increase hydropower production, which accounts for almost
40 percent of the energy produced in South Dakota. Nevertheless,
droughts are likely to become more severe in downstream states.
When droughts lower water levels enough to impair navigation,
the U.S. Army Corps of Engineers releases water from the
upstream dams, making less water available to South Dakota.
Rising Temperature and Heavy Storms
Warmer air tends to have more water vapor, so more water can
be potentially released in a storm. 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, heavy downpours will account for an increasing
fraction of ali precipitation. Larger river flows and more intense
rainstorms would each increase the risk of flooding.
Scientists do not know how the frequency and severity of tor-
nadoes 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.

Rising temperatures and changes in rainfall are likely to have
both negative and positive effects on South Dakota's farms and
ranches. Hot weather causes cows to eat less and grow more
slowly, and it can threaten their health. Increased winter and
spring precipitation could leave some fields too wet to plant, and
warmer winters may promote the growth of weeds and pests.
During drought years, hotter summers will dry the soil. Within
70 years, the frequency of days above 100°F is likely to double.
Even where ample water is available, higher temperatures
would reduce yields of corn in the warmest parts of the state.
The overall yield of corn, however, is likely to increase in cooler
parts of the Great Plains. Although higher temperatures would
reduce yields of wheat and soybeans, increased concentrations
of carbon dioxide are likely to increase yields enough to offset
the impact of higher temperatures. Increased precipitation at the
beginning of the growing season could also benefit some crops.
Warmer and shorter winters may allow for a longer growing
season, which could allow two crops per year instead of one
in some instances. Warmer winters may also benefit cattle,
offsetting some of the harm from hotter summers: during the
winter of 1996-1997, for example, high winds and heavy snow
killed half of the newborn calves and 100,000 adult cows in the
northern Great Plains.
Longer growing seasons and increased carbon dioxide con-
centrations could increase the productivity of forests. Although
forests generally benefit from higher productivity, warmer
Trees killed by a mountain pine beetle infestation in the Black Hills.
Credit: Blaine Cook US DA Forest Service.
conditions make forests more susceptible to pests. Temperature
controls the life cycle and winter mortality rates of pests such as
bark beetles, which have infested and killed trees in the Black
Hills in recent decades. With higher winter temperatures, some
pests can persist year-round, and new pests and diseases may
become established.
Human Health
Extremely hot and cold days can be unhealthy—even dangerous.
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, cardiovascular strain, and respiratory
problems. Those with low incomes may be particularly vulnerable
due to a lack of air conditioning. Power failures due to severe
weather can also present risks, especially in lightly populated
areas where access to the necessary support services may be
limited. While these risks will increase as the climate becomes
warmer, illnesses and deaths due to cold weather and snow are
likely to decline.
Climate change may also increase the length and severity of the
pollen season for allergy sufferers. For example, the ragweed
season in the northern Great Plains and Upper Midwest is now
10 to 21 days longer than it was in 1995, because the first frost
in fall is later.
A photo of a ragweed plant a common source of allergens in South
Dakota. Like many crops and pollen sources, ragweed will have a
longer growing season as temperatures rise. Stock photo.
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 Panei 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 atwww.epa.gov/climatechanae.