nited States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007J
September 1998
Climate Change And Kentucky
The earth's climate is predicted to change because human
activities are altering the chemical composition of the atmosphere
through the buildup of greenhouse gases — primarily carbon
dioxide, methane, nitrous oxide, and chlorofluorocarbons. The
heat-trapping property of these greenhouse gases is undisputed.
Although there is uncertainty about exactly how and when the
earth's climate will respond to enhanced concentrations of
greenhouse gases, observations indicate that detectable changes
are underway. There most likely will be increases in temperature
and changes in precipitation, soil moisture, and sea level, which
could have adverse effects on many ecological systems, as well
as on human health and the economy.
The Climate System
Energy from the sun drives the earth's weather and climate.
Atmospheric greenhouse gases (water vapor, carbon dioxide,
and other gases) trap some of the energy from the sun, creating
a natural "greenhouse effect." Without this effect, temperatures
would be much lower than they are now, and life as known today
would not be possible. Instead, thanks to greenhouse gases, the
earth's average temperature is a more hospitable 60°F. However,
problems arise when the greenhouse effect is enhanced by
human-generated emissions of greenhouse gases.
Global warming would do more than add a few degrees to today's
average temperatures. Cold spells still would occur in winter, but
heat waves would be more common. Some places would be drier,
others wetter. Perhaps more important, more precipitation may
come in short, intense bursts (e.g., more than 2 inches of rain
in a day), which could lead to more flooding. Sea levels would
be higher than they would have been without global warming,
although the actual changes may vary from place to place
because coastal lands are themselves sinking or rising.
The Greenhouse Effect
Solar
radiation
Some solar radiation
is reflected by the
earth and the
atmosphere
Some of the infrared radiation passes
through the atmosphere, and some is
absorbed and re-emitted in all directions
by greenhouse gas molecules. The effect
of this is to warm the earth's surface and
the lower atmosphere.
Source: U.S. Department of State (1992)
Emissions Of Greenhouse Gases
Since the beginning of the industrial revolution, human activities
have been adding measurably to natural background levels of
greenhouse gases. The burning of fossil fuels — coal, oil, and
natural gas — for energy is the primary source of emissions.
Energy burned to run cars and trucks, heat homes and busi-
nesses, and power factories is responsible for about 80% of
global carbon dioxide emissions, about 25% of U. S. methane
emissions, and about 20% of global nitrous oxide emissions.
Increased agriculture and deforestation, landfills, and industrial
production and mining also contribute a significant share of
emissions. In 1994, the United States emitted about one-fifth of
total global greenhouse gases.
Concentrations Of Greenhouse Gases
Since the pre-industrial era, atmospheric concentrations of carbon
dioxide have increased nearly 30%, methane concentrations have
more than doubled, and nitrous oxide concentrations have risen
by about 15%. These increases have enhanced the heat-trapping
capability of the earth's atmosphere. Sulfate aerosols, a common
air pollutant, cool the atmosphere by reflecting incoming solar
radiation. However, sulfates are short-lived and vary regionally,
so they do not offset greenhouse gas warming.
Although many greenhouse gases already are present in the
atmosphere, oceans, and vegetation, their concentrations in the
future will depend in part on present and future emissions.
Estimating future emissions is difficult, because they will depend
on demographic, economic, technological, policy, and institu-
tional developments. Several emissions scenarios have been
developed based on differing projections of these underlying
factors. Forexample, by 2100, in the absence of emissions control
policies, carbon dioxide concentrations are projected to be 30-
150% higher than today's levels.
Current Climatic Changes
Global mean surface temperatures have increased 0.6-1.2°F
between 1890 and 1996. The 9 warmestyears in this century all
have occurred in the last 14 years. Of these, 1995 was the warmest
year on record, suggesting the atmosphere has rebounded from
the temporary cooling caused by the eruption of Mt. Pinatubo in
the Philippines.
Several pieces of additional evidence consistent with warming,
such as a decrease in Northern Hemisphere snow cover, a
decrease in Arctic Sea ice, and continued melting of alpine
glaciers, have been corroborated. Globally, sea levels have risen
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Global Temperature Changes (1861-1996)
Year
Source: IPCC (1995), updated
4-10 inches over the past century, and precipitation over land has
increased slightly. The frequency of extreme rainfall events also
has increased throughout much of the United States.
A new international scientific assessment by the Intergovern-
mental Panel on Climate Change recently concluded that "the
balance of evidence suggests a discernible human influence
on global climate."
Future Climatic Changes
For a given concentration of greenhouse gases, the resulting
increase in the atmosphere's heat-trapping ability can be pre-
dicted with precision, but the resulting impact on climate is more
uncertain. The climate system is complex and dynamic, with
constant interaction between the atmosphere, land, ice, and
oceans. Further, humans have never experienced such a rapid rise
in greenhouse gases. In effect, a large and uncontrolled planet-
wide experiment is being conducted.
General circulation models are complex computer simulations that
describe the circulation of air and ocean currents and how energy
is transported within the climate system. While uncertainties
remain, these models are a powerful tool for studying climate. As
a result of continuous model improvements over the last few
decades, scientists are reasonably confident about the link
between global greenhouse gas concentrations and temperature
and about the ability of models to characterize future climate at
continental scales.
Recent model calculations suggest that the global surface temper-
ature could increase an average of 1.6-6.3°F by 2100, with signif-
icant regional variation. These temperature changes would be far
greater than recent natural fluctuations, and they would occur
significantly faster than any known changes in the last 10,000
years. The United States is projected to warm more than the
global average, especially as fewer sulfate aerosols are produced.
The models suggest that the rate of evaporation will increase as
the climate warms, which will increase average global precipita-
tion. They also suggest increased frequency of intense rainfall as
well as a marked decrease in soil moisture over some mid-
continental regions during the summer. Sea level is projected to
increase by 6-38 inches by 2100.
Calculations of regional climate change are much less reliable
than global ones, and it is unclear whether regional climate will
become more variable. The frequency and intensity of some
extreme weather of critical importance to ecological systems
(droughts, floods, frosts, cloudiness, the frequency of hot or cold
spells, and the intensity of associated fire and pest outbreaks)
could increase.
Local Climate Changes
Over the last century, the average temperature in Frankfort.
Kentucky, has decreased 1.4°F, and precipitation has increased
by up to 10% in many parts of the state. These past trends may or
may not continue into the future.
Over the next century, climate in Kentucky could experience
additional changes. For example, based on projections made by
the Intergovernmental Panel on Climate Change and results from
the United Kingdom Hadley Centre's climate model (HadCM2), a
model that accounts for both greenhouse gases and aerosols, by
2100 temperatures in Kentucky could increase by 3 °F (with a
range of 1-5°F) in all seasons (slightly less in summer, slightly
more in fall). Precipitation is estimated to increase only slightly in
winter (with a range of 0-10%), by 20% in spring and fall (with a
range of 10-30%), and by 30% (with a range of 10-50%) in summer.
Other climate models may show different results, especially
regarding estimated changes in precipitation. The impacts
described in the sections that follow take into account estimates
from different models. The frequency of extreme hot days in
summer would increase because of the general warming trend. It
is not clear how the severity of storms might be affected, al-
though an increase in the frequency and intensity of summer
thunderstorms is possible.
Precipitation Trends From 1900 To Present
Trends/100 years
Source: Karl et al. (1996)
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Human Health
Higher temperatures and increased frequency of heat waves may
increase the number of heat-related deaths and the incidence of
heat-related illnesses. However, some southern states appear less
susceptible to heat waves, perhaps because the population is
better adapted to the regular, intense heat.
In Louisville, one study projected a summer warming of 4-5°F
is likely to cause little change in heat-related deaths. This study
also shows that a temperature increase of 8°F could cause winter-
related deaths to increase by 20%. However, the exact reasons for
this increase are unknown. The elderly, especially those living
alone, are at greatest risk.
Climate change could increase concentrations of ground-level
ozone. For example, high temperatures, strong sunlight, and
stable air masses tend to increase urban ozone levels. A 2°F
warming, with no other change in weather or emissions, could
increase concentrations of ozone, a major component of smog, by
as much as 8%. Currently, Louisville is classified as a "moderate"
nonattainment area for ozone. Ground-level ozone is associated
with respiratory illnesses such as asthma, reduced lung function.
and respiratory inflammation. Air pollution also is made worse by
increases in natural hydrocarbon emissions such as emissions of
terpenes by trees and shrubs during hot weather. If a warmed
climate causes increased use of air conditioners, air pollutant
emissions from power plants also will increase.
Warming and other climate changes could expand the habitat
and infectivity of disease-carrying insects, thus increasing the
potential for transmission of diseases such as malaria and
dengue ("break bone") fever. Warmer temperatures could increase
the incidence of Lyme disease and other tick-borne diseases in
Kentucky, because populations of ticks, and their rodent hosts.
could increase under warmer temperatures and increased
vegetation.
Infected individuals can bring malaria to places where it does
not occur naturally. Also, some mosquitoes in Kentucky can
carry malaria. If conditions become warmer and wetter, mosquito
populations could increase, thus increasing the potential for
transmission if this and other diseases are introduced into the
area. Increased runoff from heavy rainfall could increase water-
borne diseases such as giardia, cryptosporidia, and viral and
bacterial gastroenteritides. Developed countries such as the
United States should be able to minimize the impacts of these
diseases through existing disease prevention and control
methods.
Water Resources
The Ohio River, which forms the 644-mile northern boundary of
Kentucky, is the major river in the state. Important tributaries of
the Ohio in the state include the Big Sandy, Kentucky, and Green
rivers. The Cumberland and Tennessee rivers drain small areas
along the state's southern border. These surface waters supply
most of the water needs in Kentucky. In some of the more densely
populated drainage basins, streamflows are not sufficient to meet
water requirements during dry years. Where available, reservoir
releases are needed during these low flow periods. This situation
could be exacerbated in a warmer climate. If summer rainfall
remains the same or declines, then increases in temperature and
evaporation could further reduce streamflows, lake levels, and
groundwater levels during the critical summer months. Cities such
as Frankfort and Lexington, which depend on the Kentucky River
for water supplies, could be particularly vulnerable. Lower
groundwater levels also could be detrimental for the one-third of
the population that depends on groundwater for drinking water.
Low flows and higher temperatures could worsen water quality.
which has been adversely affected in various regions of the state
by coal mining, oil and gas operations, agriculture, and domestic-
waste discharges.
Increased precipitation could alleviate water shortages and
provide more water for dilution of pollutants. However, flooding
is a recurring problem along many streams in Kentucky. Major
floods are frequent from November to May, whereas flash floods
can occur at any time. Rising groundwater levels also have
contributed to flooding in the Louisville area. Higher rainfall.
particularly during the traditional flood season, would increase
the flood risk. Increased rainfall also could increase landslides.
erosion, and levels of pesticides and fertilizers in runoff from
agricultural areas. It could also increase pollution in runoff from
mining and urban areas.
Agriculture
The mix of crop and livestock production in a state is influenced
by climatic conditions and water availability. As climate warms.
production patterns could shift northward. Increases in climate
variability could make adaptation by farmers more difficult.
Warmer climates and less soil moisture due to increased evapora-
tion may increase the need for irrigation. However, these same
conditions could decrease water supplies, which also may be
needed by natural ecosystems, urban populations, industry, and
other users.
Understandably, most studies have not fully accounted for
changes in climate variability, water availability, crop pests.
changes in air pollution such as ozone, and adaptation by
Changes In Agricultural Yield And Production
Dryland Yield Production
c
CO
6
Corn Soybeans Hay Corn Soybeans Hay
• AT = 8°F; Aprecip. = 7% • AT = 9°F; Aprecip. = 9%
Sources: Mendelsohn and Neumann (in press); McCarl (per-
sonal communication)
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farmers to changing climate. Including these factors could change
modeling results substantially. Analyses that assume changes in
average climate and effective adaptation by farmers suggest that
aggregate U.S. food production would not be harmed, although
there may be significant regional changes.
In Kentucky, production agriculture is a $3.3 billion annual
industry, almost split evenly between crops and livestock. Very
few of the farmed acres are irrigated. The major crops in the state
are corn, soybeans, and hay. Corn and soybean yields could fall
by 35% under severe conditions where temperature rises beyond
the temperature tolerance of the crop. However, under less severe
change, yields could rise by 15%. Hay and pasture yields could
rise by 30%. Estimated changes in yield vary, depending on
whether land is irrigated. Farmed acres are projected to remain
fairly constant. Livestock and dairy production may not be
affected, unless summer temperatures rise significantly and
conditions become significantly drier. Under these conditions.
livestock tend to gain less weight and pasture yields decline.
limiting forage.
Forests
Trees and forests are adapted to specific climate conditions.
and as climate warms, forests will change. These changes could
include changes in species composition, geographic range, and
health and productivity. If conditions also become drier, the
current range of forests could be reduced and replaced by
grasslands and pasture. Even a warmer and wetter climate
could lead to changes; trees that are better adapted to warmer
conditions, such as oaks and pines, would prevail. Under these
conditions, forests could become more dense. These changes
could occur during the lifetimes of today's children, particularly if
the change is accelerated by other stresses such as fire, pests,
and diseases. Some of these stresses would themselves be
worsened by a warmer and drier climate.
With changes in climate, the extent of forested areas in Kentucky
could change little or decline by as much as 10-25%. However, the
types of trees dominating those forests and woodlands are likely
to change. Forested areas could be increasingly dominated by
pine and scrub oaks, replacing many of the eastern hardwoods
common throughout eastern Kentucky. In areas where richer soils
are prevalent, southern pines could increase their range and
density, and in areas with poorer soils, which are more common in
Kentucky's forests, scrub oaks of little commercial value
Changes In Forest Cover
Current +10°F, +13% Precipitation
• Conifer Forest
I Broadleaf Forest
Savanna/Woodland
Sources: VEMAP Participants (1995); Neilson (1995)
(e.g., post oak and blackjack oak) could increase their range. As a
result, the character and diversity of Kentucky forests could
change. Climate change could also affect the success of tree
plantings to stabilize open-face mining sites.
Ecosystems
Kentucky consists of three major geographic areas and has
more running water than any other state except Alaska. As a
result, Kentucky is home to many diverse ecosystems. In the
west, the Gulf Coastal Plain is bounded by the Mississippi.
Ohio, and Tennessee rivers (the last is now Kentucky Lake).
The bottomland hardwood forests of this area include some of
the Mississippi Delta's last intact bald cypress-tupelo swamps.
and are home to many rare, threatened, or endangered plants
and animals, including the globally imperiled Rockcastle aster and
a diverse array of freshwater mussels. Thousands of waterfowl.
particularly wood ducks, overwinter in this region. Climate
change could exacerbate the current threats to ecosystems of
this region, including increases in exotic species invasions.
nutrient and toxic loading, and sedimentation. If increases in
evaporation exceed increases in precipitation during the summer
months, streams could shift from constant to intermittent flows.
thereby favoring plants and animals adapted to these conditions
(e.g., chironomids and mayflies), rather than those with relatively
long life cycles (e.g., caddisflies and mollusks). Under a warmer
climate, the habitat available to coldwater fish species such as
trout could decrease, thus limiting their abundance and distribu-
tion. Higher flood peaks, caused by greater clustering of storms.
could increase erosion and sediment loading to stream channels.
The extent and duration of inundation is crucial to the health of
wetlands, including productivity, decomposition, and cycling
of major nutrients and pollutants.
The southeastern border of the state is characterized by
Appalachian oak forests. The oaks of high-elevation forests are
already declining because of the increasing incidence of several
pests. An example is the shoestring fungus, which appears to be
associated with drought conditions. Climate change could
accelerate these declines. A native grassland region called the
Big Barrens is another well-known ecological community. In
this ecosystem, climate change could favor the spread of exotic
weedy species, which spread and adapt easily.
Kentucky is also well known for its karst features, including
Mammoth Cave, the world's longest cave. Caves are important
geological, hydrological, and biological resources that provide
habitat for huge populations of bats (including the endangered
gray and Indiana bats) and numerous invertebrate species.
Higher-than-normal winter temperatures could boost tempera-
tures inside cave bat roosting sites, which has been shown to
cause higher mortality due to increased winter body weight loss
in endangered Indiana bats (e.g., an increase of 9°F during winter
hibernation has been associated with a 42% increase in the rate of
body mass loss).
For further information about the potential impacts of climate
change, contact the Climate and Policy Assessment Division
(2174), U.S. EPA, 401 M Street SW, Washington, DC 20460, or
visit http://www. epa.gov/globalwarming/impacts.
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