A United States
Environmental Protection
\0 J 1 Agency
August 2016
What Climate Change

moot* for Kentucky

Kentucky's climate is changing. Although the average
temperature did not change much during the 20th century,
most of the commonwealth has warmed in the last
20 years. Average annual rainfall is increasing, and a
rising percentage of that rain is falling on the four wettest
days of the year. In the coming decades, the changing
climate is likely to reduce crop yields and threaten some
aquatic ecosystems. Floods may be more frequent, and
droughts may be longer, which would increase the
difficulty of meeting the competing demands for water in
the Ohio, Tennessee, and Cumberland rivers.
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 (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.
Natural cycles and sulfates in the air prevented much of
Kentucky from warming during the last century. Sulfates
are air pollutants that reflect sunlight back into space.
Now sulfate emissions are declining, and the factors that
once prevented Kentucky from warming are unlikely to
Temperature change (°F):
Rising temperatures in the last century. Kentucky has warmed
less than most of the United States. Source: EPA, Climate
Change Indicators in the United States.
Flooding at Third and Magnolia Streets in Louisville after heavy rains in
August 2009. Credit: Mike Howard, courtesy of the National Weather
Seivice and the Louisvilie and Jefferson County Metropolitan Sewer District.
Precipitation and Water Resources
Annual precipitation in Kentucky has increased approximately
5 percent since the first half of the 20th century. But rising tem-
peratures increase evaporation, which dries the soil and decreases
the amount of rain that runs off into rivers. Although rainfall during
spring is likely to increase during the next 40 to 50 years, the
total amount of water running off into rivers or recharging ground
water each year is likely to decline 2.5 to 5 percent, as increased
evaporation offsets the greater rainfall. Droughts are likely to be
more severe, because periods without rain will be longer and very
hot days will be more frequent.
Flooding, Navigation, and Hydroelectric Power
Flooding is becoming more severe in the Southeast. 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. The Tennessee Valley
Authority (TVA) and the U.S. Army Corps of Engineers operate
Kentucky Dam, Wolf Creek Dam, and other dams to prevent serious
floods on the Ohio, Tennessee, and Cumberland rivers. The agencies
release water from the reservoirs behind these dams before the
winter flood season. By lowering water levels, these releases
provide greater capacity for the reservoirs behind those dams
to prevent flooding. Nevertheless, dams and other flood control
structures cannot prevent all floods. The Ohio River has flooded
Louisville several times, for example, and flash floods have caused
property destruction and deaths throughout Kentucky.

Increasingly severe droughts could pose challenges for river
transportation. The drought of 2005 closed portions of the lower
Ohio River to commercial navigation, which delayed shipments of
crops and other products between Kentucky and the Mississippi
River. In 2012, a drought caused navigation restrictions on the
lower Mississippi River, which cost the region more than
$275 million.
A barge passes by Paducah during a period of low water on the Ohio
River in summer 2005. Drought conditions caused shipping delays
throughout the region. Credit: National Weather Service.
Droughts also affect the amount of electricity from hydroelectric
dams. During the 2007 drought, total production from the TVA's
hydroelectric plants fell by more than 30 percent, which forced
the TVA to meet customer demand by using more expensive
fuel-burning power plants.
Aquatic Ecosystems
Changing climate can harm aquatic ecosystems. Warmer water
lowers the level of dissolved oxygen in surface water, which can
severely limit fish populations. Because fish cannot regulate their
body temperatures, warmer water can make a stream uninhab-
itable for fish that require cooler water. Warmer temperatures
can also increase the frequency of algal blooms, which can be
toxic and further reduce dissolved oxygen. Summer droughts
may amplify these effects, while periods of extreme rainfall can
increase the impacts of pollution on streams.
Longer frost-free growing seasons and increased concentrations
of atmospheric carbon dioxide tend to increase yields for many
crops during an average year. But more severe droughts and
more hot days are likely to reduce yields, especially in the
western half of Kentucky, which in seventy years is likely to have
15 to 30 more days with temperatures above 95°F than it has
today. Even on irrigated fields, higher temperatures are likely to
reduce yields of corn, and possibly soybeans. Higher
temperatures are also likely to reduce livestock productivity: hot
weather causes cows to eat less, grow more slowly, and
produce less milk, and it can threaten their health.
Forest Resources
Higher temperatures and changes in rainfall are unlikely to
substantially reduce forest cover in Kentucky, but the composition
of those forests may change. More droughts would reduce forest
productivity, and ciimate change is also likely to increase the
damage that insects and diseases cause to forests. Yet longer
growing seasons and increased carbon dioxide concentrations
could more than offset the losses from those factors. In central
Kentucky, the population of maple, beech, and birch trees is likely
to decline, in favor of the oak and hickory trees that dominate
forests in most of the state.
Human Health
Hot days can be unhealthy—even dangerous. High air tem-
peratures can cause heat stroke and dehydration, and affect
people's cardiovascular and nervous systems. Certain people are
especially vulnerable, including children, the elderly, the sick,
and the poor. Higher 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 Kentucky Department for
Environmental Protection have been working to reduce ozone
concentrations. As the climate changes, continued progress
toward clean air will require even more reductions in the air
pollutants that contribute to ozone.
The sources of information about climate and the impacts of ciimate 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.Qov/ciimatechanc.ie.