United States
Environmental Protection
Agency
Office of Policy, Planning
and Evaluation
(2111)
EPA 230-F-97-008m
September 1997
«>EPA Climate Change And Illinois
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 enhancedby
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
Some solar radiation
is reflected by the
earth and the
k 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 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
Source: U.S. Department of State (1992)
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Global Temperature Changes (1861-1996)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
r^ 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 Decatur, Illinois.
has decreased 0.2°F, and precipitation has increased by up to
20% in many parts of the state.
Over the next century, climate in Illinois 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 Illinois could increase by about 2°F in
summer (with a range of 1-4°F), 3°F in winter and spring (with a
range of 1-7°F), and 4°F in fall (with a range of 2-9°F). Precipita-
tion is estimated to increase by about 10% in winter and spring.
15-50% in fall, and 25-70% in summer. Other climate models
show different results, with winter precipitation increasing more
than summer precipitation. The amount of precipitation on
extreme wet days is likely to increase, especially in summer. 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
Water Resources
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. Illinois, with its irregular, intense heat
waves, could be especially susceptible.
In Chicago, one study projects that by 2050 heat-related deaths
during a typical summer could increase 85%, from about 190
heat-related deaths per summer to nearly 360 (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 Chicago
area is classified as a "severe" 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 Illinois, 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 northward the region where these mosquitoes
breed and overwinter. If conditions become warmer and wetter.
mosquito populations could increase, thereby increasing the risk
of transmission of these diseases.
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.
Most of Illinois drains into the Mississippi River, which forms the
state's western boundary. Tributaries include the Illinois River.
the Rock River, and several smaller rivers. A small portion of the
eastern part of the state drains into the Wabash River. Fall and
spring rains largely determine runoff in the major tributaries and.
to a lesser degree, spring snowmelt. Warmer temperatures would
result in less snow, earlier snowmelt, and increased summer
evaporation. Hence, winter runoff could increase, and summer
and fall runoff could decrease. Changes in summer and fall runoff
depend on changes in rainfall, which could either increase or
decrease. With a drier climate, irrigation needs for agriculture
could increase, whereas wetter conditions could exacerbate local
flooding. Increased evaporation along with less rainfall could
reduce recharge of groundwater aquifers, while increased rainfall
could contribute to recharge.
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
Corn Soybeans
• AT = 9°F; Aprecip. = 4%
Corn Soybeans
AT = 9°F; Aprecip. = 16%
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
farmers suggest that aggregate U.S. food production would not be
harmed, although there may be significant regional changes.
In Illinois, agriculture is an $8 billion annual industry, three-
fourths of which comes from crops. Very little of the crop acreage
is irrigated. The major crops in the state are corn and soybeans.
Irrigated and dryland yields of corn could change little or be
reduced by as much as 32%, while soybean yields could vary
from a drop of 24% to an increase of 13%. This could lead to
changes in acres farmed and production. For example, corn yields
could rise while production falls because of a decrease in corn
acres farmed.
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 Illinois
may change little or could increase by as much as 10-40%.
depending on competition from agricultural uses. In addition to
competition, the uncertainties depend on many other factors.
including whether soils become drier and, if so, how much drier.
With hotter, drier weather, southern pines gradually could replace
deciduous forests in the southern part of the state, particularly in
areas with rich soils. In areas with poorer soils, which are more
common in Illinois forests, scrub oaks of little commercial value
(e.g., post oak and blackjack oak) could increase. In contrast.
warmer, wetter conditions could expand northward the range of
deciduous forests.
Changes In Forest Cover
+10°F, +13%
Current Precipitation
| Broadleaf Forest
| Savanna/Woodland
Grassland
Source: VEMAP Participants (1995); Neilson (1995)
Ecosystems
The forests and woodlands of Illinois support a variety of
animals, including 80% of the mammals, 60% of the birds, and
80% of the amphibians and reptiles that inhabit the state. Climate
change could cause substantial shifts in the ranges that support
these species, perhaps leading to some migration of species.
which would be difficult because of fragmented land use patterns.
Warmer winter temperatures could increase insect populations
and plant disease that could affect adversely forest ecosystems.
Prairies support 117 of the nearly 500 plant and animal species
considered endangered or threatened in Illinois. Because of the
extensive fragmentation of Illinois' prairies, it could be difficult
for some species to migrate in response to climate change.
Wetlands such as the riparian habitats along the Mississippi.
Ohio, and other rivers and streams could be especially sensitive
to climate change. Changes in precipitation could affect flooding
patterns and availability of nutrients. Aquatic species that are
sensitive to water temperature could be affected adversely by
climate change. Habitat for fish such as smallmouth bass,
walleye, and northern pike could be reduced.
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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