A	United States
Environmental Protection
LI M % Agency
What Climate Change
Means for Mississippi
In the coming decades, Mississippi will become warmer, and both
floods and droughts may be more severe. Unlike most of the nation,
Mississippi did not become warmer during the last 50 to 100 years.
But soils have become drier, annual rainfall has increased, more rain
arrives in heavy downpours, and sea level is rising about one inch
every seven years. The changing climate is likely to increase
damages from tropical storms, reduce crop yields, harm livestock,
increase the number of unpleasantly hot days, and increase the risk
of heat stroke and other heat-related illnesses.
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 atmo-
sphere of our planet about one degree (F) 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, natural cycles and sulfates in the air cooled
Mississippi. Sulfates are air pollutants that reflect sunlight back into
space. Now sulfate emissions are declining, and the factors that once
prevented the state from warming are unlikely to persist.
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. 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.
Temperature change (°F):
-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5
Rising Seas and Retreating Shores
Sea level is rising more rapidly in Mississippi than most
coastal areas because the land is sinking. If the oceans
and atmosphere continue to warm, sea level along the
Mississippi coast is likely to rise between twenty
inches and four feet in the next century. Rising sea
level submerges wetlands and dry land, erodes
beaches, and exacerbates coastal flooding. Coastal
communities along Mississippi Sound are protected by
undeveloped barrier islands, so erosion of those
islands could threaten communities on the mainland.
Storms, Homes, and Infrastructure
Tropical storms and hurricanes have become more
intense during the past 20 years. Although warming
oceans provide these storms with more potential
energy, scientists are not sure whether the recent
intensification reflects a long-term trend. Nevertheless,
hurricane wind speeds and rainfall rates are likely to
increase as the climate continues to warm.
Changing temperatures in the last century. While most of the nation has
warmed, Mississippi and a few other states have cooled. Source: EPA,
Climate Change Indicators in the United States.
Hurricane Katrina's storm surge and high winds destroyed the
homes on these three lots in Long Beach, and many others.
Credit: John Fleck, FEMA.

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Whether or not storms become more intense, coastal
homes and infrastructure will flood more often as sea level
rises, because storm surges will become higher as well.
Rising sea level is likely to increase flood insurance rates,
while more frequent storms could increase the deductible
for wind damage in homeowner insurance policies. Many
cities, roads, railways, ports, airports, and oil and gas
facilities along the Gulf Coast are vulnerable to the
combined impacts of storms and sea level rise. People may
move from vulnerable coastal communities and stress the
infrastructure of the communities that receive them.
Flooding and River Transportation
Changing the climate is also likely to increase inland
flooding. Vicksburg and Natchez are vulnerable to high
water levels on the Mississippi River. Since 1958, the
amount of precipitation during heavy rainstorms has
increased by 27 percent in the Southeast, and the trend
toward increasingly heavy rainstorms is likely to continue.
Moreover, streamflows in the Midwest are increasing,
and the amount of rainfall there is also likely to increase,
which could increase flooding in Mississippi, because
most of the Midwest drains into the Mississippi River.
Droughts create a different set of challenges. During severe
droughts in the Mississippi River's watershed, low flows
can restrict commercial navigation. For example, low water
in 2012 forced the U.S. Army Corps of Engineers to reduce
allowable barge sizes on the Mississippi River and close
the river at Greenville for more than a week, which delayed
approximately 100 barges.
The Mississippi River flooded parts of Vicksburg in May 2011,
including the old railroad depot shown here. Credit: Patrick Moes,
U.S. Army Corps of Engineers.
Agriculture
Changing the climate will have both harmful and beneficial
effects on farming. Seventy years from now, Mississippi is
likely to have 30 to 60 days per year with temperatures above
95°F, compared with about 15 days today. Even during the
next few decades, hotter summers are likely to reduce yields
of corn. But higher concentrations of atmospheric carbon
dioxide increase crop yields, and that fertilizing effect is likely
to offset the harmful effects of heat on soybeans, cotton,
wheat, and peanuts—if enough water is available. More
severe droughts, however, could cause crop failures. Higher
temperatures are also likely to reduce livestock productivity,
because heat stress disrupts the animals' metabolism.
Forest Resources
Higher temperatures and changes in rainfall are unlikely to
substantially reduce forest cover in Mississippi, although the
composition of trees in the forests may change. More
droughts would reduce forest productivity, and climate
change is also likely to increase the damage from insects
and disease. But longer growing seasons and higher carbon
dioxide concentrations could more than offset the losses
from those factors. Forests cover almost two-thirds of the
state. Oak, hickory, and white pine trees are most common
in the northern part of the state, except along the Mississippi
River delta. In the southern part of the state, loblolly and
longleaf pines are most common. As the climate warms,
forests in southern Mississippi are likely to have more oaks
and white pines, and fewer loblolly and longleaf pines.
Human Health
Hot days can be unhealthy—even dangerous. Certain people
are especially vulnerable, including children, the elderly,
the sick, and the poor. High air temperatures can cause
heat stroke and dehydration and affect people's cardio-
vascular and nervous systems. Warmer air 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
Mississippi Department of Environmental Quality have been
working to reduce ozone concentrations. As the climate
changes, continued progress toward clean air will become
more difficult.
The sources of information about ciimate 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 www.epa.aov/climatechanae.

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