United States
Environmental Protection
Agency
Office of Policy, Planning
and Evaluation
(2111)
EPA 230-F-97-008y
September 1997
&EPA Climate Change And Missouri
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 under way. 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
passes
through
the clear
atmosphere
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.
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 businesses,
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, common
air pollutants, cool the atmosphere by reflecting incoming solar
radiation. However, sulfates are short-lived and vary regionally.
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. 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 warmest years in this century all
have occurred in the last 14 years. Of these, 1995 was the
warmest year on record, suggesting the atmosphere has re-
bounded from the temporary cooling caused by the eruption of
Mt. Pinatubo hi 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
Source: U.S. Department of State (1992)
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Global Temperature Changes (1861-1996)
UtO
0.4
0,2
0
-0.2
-0,4
=0,6
-0.8
,1
pS
J
A r
/ VA/V
/
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/
/\ -f-L **•*
/x/vn ry
/ ^ \r
y
V
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 uncertain-
ties 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 tempera-
ture 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 Jefferson City,
Missouri, has decreased 0.5°F, and precipitation has increased by
up to 10% in many parts of the state.
Over the next century, climate in Missouri 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 Missouri could increase by about 2°F in
summer (with a range of 1-4°F) and about 3°F in the other
seasons (with a range of 1-7°F). Little change is estimated for
winter precipitation. Increases of about 15% are estimated for
spring and fall, and the summer increase is estimated to range
between 20 and 60%. Other climate models may show different
results, with winter precipitation increasing more than summer
precipitation. The amount of precipitation on extreme wet days in
summer is likely to increase. The frequency of extreme hot days
in summer would increase because of the general warming trend.
Although it is not clear how severe storms would change, an
increase in the frequency and intensity of summer thunderstorms
is possible.
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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Climate Change Impacts
Global climate change poses risks to human health and to
terrestrial and aquatic ecosystems. Important economic resources
such as agriculture, forestry, fisheries, and water resources also
may be affected. Warmer temperatures, more severe droughts and
floods, and sea level rise could have a wide range of impacts. All
these stresses can add to existing stresses on resources caused by
other influences such as population growth, land-use changes,
and pollution.
Similar temperature changes have occurred in the past, but the
previous changes took place over centuries or millennia instead
of decades. The ability of some plants and animals to migrate and
adapt appears to be much slower than the predicted rate of
climate change.
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. Missouri, with its irregular, intense heat
waves, could be especially susceptible.
In St. Louis, one study projects that by 2050 heat-related deaths
during a typical summer could increase 170%, from about 80
heat-related deaths per summer to over 200 (although increased
air conditioning use may not have been fully accounted for).
Winter-related deaths are expected to change very little. The
elderly, particularly 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. Air
pollution also is made worse by increases in natural hydrocarbon
emissions during hot weather. If a warmed climate causes
increased use of air conditioners, air pollutant emissions from
power plants also will increase.
A 4°F warming in the Midwest, with no other change in weather
or emissions, could increase concentrations of ozone, a major
component of smog, by as much as 8%. Currently, the St. Louis
area is classified as a "moderate" nonattainment area for ozone.
Ground-level ozone has been shown to aggravate respiratory
illnesses such as asthma, reduce existing lung function, and
induce respiratory inflammation. In addition, ambient ozone
reduces crop yields and impairs ecosystem health.
Warming and other climate changes may 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. Mosquitos flourish in Missouri, and some
carry St. Louis encephalitis. Also, the mosquitoes that carry
dengue fever, Eastern equine encephalitis, and LaCrosse en-
cephalitis recently have spread as far north as Chicago. Global
warming could shift farther north the region where these mosqui-
toes breed and overwinter. If conditions become warmer and
wetter, mosquito populations could increase, thereby increasing
the risk of transmission of these diseases.
Water Resources
Water resources are affected by changes in precipitation as well
as by temperature, humidity, wind, and sunshine. Changes in
streamflow tend to magnify changes in precipitation. Water
resources in drier climates tend to be more sensitive to climate
changes. Because evaporation is likely to increase with warmer
climate, it could result in lower river flow and lower lake levels,
particularly in the summer. If streamflow and lake levels drop,
groundwater also could be reduced. In addition, more intense
precipitation could increase flooding.
The Missouri River drams about two-thirds of the state.
The remainder of the rivers in the state drain directly to the
Mississippi River, except a few in the southern portion of
the state that drain into the Arkansas River. The Missouri,
Mississippi, and Arkansas are all large rivers, whose flows are
mostly generated outside and well upstream of the state (for
example, in Montana and Wyoming). Increased rainfall could
lead to localized flooding. However, summer flows could be
reduced considerably if summer rainfall decreases. These
conditions could present a range of problems for municipal
and industrial water supply, as well as for instream water uses
such as navigation and recreation.
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 sectors.
Changes In Agricultural Yield And Production
Irrigated Yield Production
40
30
CD
g 20
OJ
6
3s 10
o
Corn Soybeans Hay
• AT = 9°F; Aprecip. = 2%
Corn Soybeans Hay
AT = 8°F; Aprecip. = 17%
Source: Mendelsohn and Neumann (in press); McCarl (personal
communication) ,
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Understandably, most studies have not fully accounted for
changes in climate variability, water availability, and imperfect
responses by farmers to changing climate. Including these factors
could change modeling results substantially. Analyses that
assume changes in average climate and effective adaptation by
fanners suggest that aggregate U.S. food production would not be
harmed, although there may be significant regional changes.
In Missouri, agriculture is a $4 billion annual industry, one-half
of which comes from livestock, especially cattle. Less than 10%
of the crop acreage is irrigated. The major crops in the state are
corn, soybeans, and hay. Corn and soybean yields could fall by as
much as 22% or rise by as much as 6%, depending on whether
irrigation is used. Hay yields could increase by about 30%. These
yield changes could lead to changes in acres farmed and produc-
tion. For example, corn yields could increase only slightly while
production rises substantially because of an increase in corn acres
farmed.
Changes In Forest Cover
Current +10°F, +13% Precipitation
ItvPf,*^'- - - fVMt • '>- -' T " • 'Srw-'f --
m
Broadleaf Forest
Savanna/Woodland
Grassland
Source: VEMAP Participants (1995); Neilson (1995)
Forests
Trees and forests are adapted to specific climate conditions, and
as climate warms, forests will change. These changes could
include changes in species, geographic range, and health and
productivity. If conditions also become drier, the current range
and density of forests could be reduced and replaced by grass-
lands and pasture. Even a warmer and wetter climate could lead
to changes; trees that are better adapted to warmer conditions,
such as oaks and southern pines, would prevail. Under these
conditions, forests could become more dense. These changes
could occur during the lifetimes of today's children, particularly
if 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 Missouri
could change little or decline by as much as 10-20%. The
uncertainties depend on many factors, including whether soils
become drier and, if so, how much drier. Hotter, drier weather
could increase the frequency and intensity of wildfires, whereas
increased rainfall could reduce their severity. In areas with richer
soils, the range and density of southern pines could increase and
become more dominant within the oak and hickory forests that
predominate in southern Missouri and in the Ozarks. In areas
with poorer soils, which are more common in Missouri's forest-
lands, scrub oaks of little commercial value (e.g., post oak and
blackjack oak) could increase. Grasslands and savanna eventually
could replace forests and woodlands in northern Missouri. These
changes would significantly affect the character of Missouri
forests and the activities that depend on them.
Ecosystems
Ecosystems in Missouri include extensive forests, rivers, streams,
and prairies. The Ozark Mountains contain several rivers
designated as "Wild and Scenic" by Congress; these rivers also
provide winter habitat for many bald eagles. Riparian and stream
ecosystems are especially sensitive to changes in rainfall. Water
temperature changes caused by climate change could reduce
habitat for smallmouth bass, northern pike, and other species such
as walleye and yellow perch.
Changes in temperature and rainfall could shift the types and
locations of habitats and ecosystems, in particular, the tallgrass
prairies. Climate change could increase pressure on Missouri
prairie lands from non-native plants. Prairie State Park, which is
Missouri's largest remaining tallgrass prairie, provides habitat for
approximately 150 bird species and 25 rare or endangered
species. The park also contains Missouri's most pristine prairie
headwater stream, East Drywood Creek, and wildlife such as the
American bison, elk, greater prairie chicken, northern harrier,
upland sandpiper, scissor-tailed flycatcher, and coyote. The
fragmented prairie could impede migration of some plants and
animals vulnerable to climate change.
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.
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