United States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007a
September 1998
Climate Change And Alabama
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
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
institutional developments. Several emissions scenarios have
been developed based on differing projections of these under-
lying factors. For example, 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 out-
breaks) could increase.
Local Climate Changes
Over the last century, the average temperature in Tuscaloosa.
Alabama, has decreased 0.1°F, and precipitation has increased by
up to 20% in many parts of the state. These past trends may or
may not continue into the future.
Over the next century, climate in Alabama 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 Alabama could increase by 2°F in winter
and summer (with a range of 1 -4°F), 3 °F in spring (with a range
of 1-5°F), and4°F infall (witharangeof 2-7°F). Precipitation is
estimated to change little in winter, increase by 10% in spring
(with a range of 5-20%), and increase by 15% in summer and fall
(with a range of 5-30%). 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
such as hurricanes might be affected, although an increase in the
frequency and intensity of summer thunderstorms is possible.
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. The elderly, particularly those living alone.
Precipitation Trends From 1900 To Present
Trends/100 years
+20%
+10% £
+5% •
-5% O
-10% O
-20%
Source: Karl et al. (1996)
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are at greatest risk. One study, which included Birmingham, found
that populations in some southern states are used to regular.
intense heat; therefore, little change in the number of heat-related
deaths (currently about 40 in Birmingham) is expected.
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. Currently.
Birmingham is classified as a moderate "nonattainment" area for
ozone (but only marginally). Increased temperatures could
increase ozone concentrations further. Ground-level ozone is
associated with respiratory illnesses such as asthma, reduced
lung function, and respiratory inflammation.
Infected individuals can bring malaria to places where it does
not occur naturally. Also, some mosquitoes in Alabama can carry
malaria, and others can carry eastern equine encephalitis, which
can be lethal or cause neurological damage. If conditions become
warmer and wetter, mosquito populations could increase, thus
increasing the risk of transmission if these diseases are intro-
duced into the area. Increased runoff from heavy rainfall could
increase water-borne diseases such as giardia, cryptosporidia.
and viral and bacterial gastroenteritides. Rodent populations that
carry hantavirus and leptospirosis (a bacterium) are sensitive to
climatic factors. Drought can reduce rodent predators (owls.
snakes, coyotes), and sudden rains can bring new food supplies
to rodents. These conditions could be associated with upsurges
of rodent populations. In addition, warmer seas could contribute
to the increased intensity, duration, and extent of harmful algal
blooms, that is, red tides. These blooms damage habitat and
shellfish nurseries, can be toxic to humans, and can carry bacteria
like those causing cholera.
Developed countries such as the United States should be able to
minimize the impacts of these diseases through existing disease
prevention and control methods.
Coastal Areas
Sea level rise could lead to flooding of low-lying property.
loss of coastal wetlands, erosion of beaches, saltwater contami-
nation of drinking water, and decreased longevity of low-lying
roads, causeways, and bridges. In addition, sea level rise
could increase the vulnerability of coastal areas to storms
and associated flooding.
Alabama has a 600-mile tidally influenced shoreline along the
Gulf of Mexico. The shoreline consists of a low-lying coastal
plain, narrow barrier islands, forested swamps, and low terraces.
Along much of the Florida Panhandle and Alabama Gulf coast.
sea level already is rising by approximately 9 inches per century.
and it is likely to rise another 20 inches by 2100. Possible re-
sponses to sea level rise include building walls to hold back the
sea, allowing the sea to advance and adapting to it, and raising
the land (e.g., by replenishing beach sand, elevating houses
and infrastructure). Each of these responses will be costly.
either in out-of-pocket costs or in lost land and structures. For
example, the cumulative cost of sand replenishment to protect
the coast of Alabama from the estimated sea level rise by 2100 is
$60-$220 million. However, sand replenishment may not be cost-
effective for all coastal areas in the state, and therefore some
savings could be possible.
Water Resources
In a warmer climate runoff would be influenced primarily by
higher temperatures, increased evaporation, and changes in
precipitation. Reduced runoff and lower groundwater levels in the
summer could affect the availability of water to satisfy Alabama's
growing and competing needs for municipal, industrial, irrigation.
and recreational uses of water. Large groundwater withdrawals in
the coastal zones of Baldwin and Mobile counties, which include
the Mobile Bay and Gulf Shores regions, have increased salinity
in wells due to saltwater intrusion into the aquifers. An increase
in sinkhole formation has also been associated with growing
groundwater withdrawals. Warmer and drier conditions, particu-
larly if accompanied by rising sea levels, could compound these
types of problems due to higher demand and lower flows.
Lower flows and higher temperatures could also degrade water
quality by concentrating pollutants and reducing the assimilation
of wastes. One of the largest offstream uses of water in Alabama
is thermoelectric power generation. Higher water temperatures
could reduce the efficiency of industrial and power plant cooling
systems and might make it increasingly difficult to meet regula-
tory standards for acceptable downstream water temperatures.
particularly during extremely warm periods. Increases in precipita-
tion would alleviate these impacts. However, higher rainfall.
particularly during the traditional winter-spring flood season.
could contribute to localized flooding and increased levels of
pesticides and fertilizers in runoff from agricultural 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
Changes In Agricultural Yield And Production
Dryland Yield Production
Cotton Corn Hay
• AT = 8°F; Aprecip. = 3%
Cotton Corn Hay
AT = 7°F; Aprecip. = -6%
Sources: Mendelsohn and Neumann (in press); McCarl
(personal communication)
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evaporation 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 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 Alabama, production agriculture is a $3 billion annual industry.
two thirds of which comes from livestock, mainly poultry. Very
few of the farmed acres are irrigated. The major crops in the state
are cotton, corn, and hay. Climate change could leave cotton
yields essentially unchanged, and corn yields could rise by 7%
or fall by 9%, depending on how climate changes. Hay yields are
projected to rise 5-19%. Farmed acres are projected to fall 29-54%
as a result of changes in farm production and prices. Livestock
and dairy production may not be affected, unless summer
temperatures rise significantly and conditions become signifi-
cantly 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 condi-
tions, such as subtropical evergreens, would prevail over time.
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
Changes In Forest Cover
Current +10°F, +13% Precipitation
• Conifer Forest
• Broadleaf Forest
Savanna/Woodland
Sources: VEMAP Participants (1995); Neilson (1995)
themselves be worsened by a warmer and drier climate. Commer-
cial timber production could also be affected by resulting
changes in growth rates, plantation acreage and management.
and market conditions.
In Alabama, longleaf and slash pine forests could expand
northward and replace some of the loblolly and shortleaf pine
forests. Wetter conditions would favor expansion of southern
pine forests, as well as oak and hickory forests and the gum and
cypress forests found along the Gulf Coast. In contrast, under
drier conditions, 40-70% of forests in the east-central part of the
state could be replaced by grasslands and pasture. Warmer and
drier conditions could increase the frequency and intensity of
fires, which could result in increased losses to important commer-
cial timber areas. Even warmer and wetter conditions could stress
forests by increasing the winter survival of insect pests.
Ecosystems
Alabama is located at the intersection of several geographic
areas, and its ancient and complex geological terrain is home to
a variety of ecosystems, ranging from the Appalachians in the
north to the coastal plain in the south. Although it ranks 29th of
all the states in area, it is the nation's fourth in terms of plant and
animal species richness. With 235,000 miles of waterways
spanning three major river basins (the Mobile, Tennessee, and
Apalachicola), its aquatic biodiversity is particularly notable.
Freshwater fauna in the rivers and streams include 52% of North
America's known freshwater turtles (of these, 22% are endemic to
the state), 38% (41% endemic) of freshwater fishes, 60% (34%
endemic) of mussels, and 43% (77% endemic) of all gill-breathing
snails. The Cahaba River, Alabama's longest free-flowing river.
is home to 131 species offish, the greatest diversity for any river
of its size on the continent. Habitat for warmwater fish could be
reduced by hotter temperatures. Alabama's coastline may be
small in comparison to other Gulf Coast states, but over 500
species of marine mollusks have been found in the coastal
sands and waters of Alabama.
Climate change could exacerbate threats to coastal and freshwater
ecosystems. For example, warmer air temperatures could lead to
reduced stream flow and warmer water temperatures, which would
significantly impair reproduction offish and other animals and
favor the spread of exotic species that exhibit a high tolerance for
extreme environmental conditions. The low-lying Mississippi
Delta is particularly vulnerable to the effects of sea level rise —
inundation of coastal lands, intrusion of saltwater into coastal
freshwater ecosystems, and increases in erosion rates and storm
damage resulting from increased storm frequency. If rainfall
increases, runoff along the Gulf Coast and the rate of estuarine
flushing are expected to increase, leading to reduced yields in
shrimp and other species favoring high salinities. Higher runoff
rates and outflow into the Gulf of Mexico could increase nutrient
loads and alter water temperatures, exacerbating the already
serious eutrophication and hypoxia.
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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