United States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007S
September 1998
Climate Change And Ohio
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.
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.
Some solar radiation
is reflected by the
earth and the
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
1
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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 near Columbus.
Ohio, has increased 0.3°F, and precipitation has increased by up
to 10% in this and other parts of the state, and declined by up to
10% in the southern part of the state. These past trends may or
may not continue into the future.
Over the next century, climate in Ohio may experience additional
changes. For example, based on projections made by the Inter-
governmental 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 Ohio could increase by 3 °F in winter, spring.
and summer (with a range of 1 -6°F) and 4°F in fall (with a range of
2-7°F). Precipitation is estimated to increase by 15% in winter and
spring (with a range of 5-25%), 20% infall (with a range of 10-
35%), and 25% (with a range of 10-40%) 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 is expected to
increase along with the general warming trend. It is not clear how
the severity of storms 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. Ohio, with its irregular, intense heat
waves, could be susceptible.
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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One study projects that heat-related deaths could nearly double
inboth Cleveland and Columbus given a 4°F warming, from about
30 to 60 (although increased air conditioning use may not have
been fully accounted for). In Cincinnati, summer deaths are
estimated to nearly triple with a warming of 3°F, from 14 to 42. The
elderly, especially those living alone, are at greatest risk. This
study also projects little change in winter-related deaths in
Cleveland, Columbus, and Cincinnati.
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 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%. Perhaps more important.
however, is that the area exceeding national health standards
for ozone could increase. Currently, Cincinnati is classified as a
"moderate" nonattainment area for ozone, and increased tempera-
tures could increase ozone concentrations further. 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 emis-
sions 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. Upper and lower respiratory allergies also are
influenced by humidity. A 2°F warming and wetter conditions
could increase respiratory allergies.
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. Infected individuals can bring malaria to
places where it does not occur naturally. Also, some mosquitoes
in Ohio can carry California and St. Louis 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
introduced into the area.
Warmer temperatures could increase the incidence of Lyme
disease and other tick-borne diseases in Ohio, because popula-
tions of ticks, and their rodent hosts, could increase under
warmer temperatures and increased vegetation. 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 availability of water has helped Ohio develop a diverse
economy: agriculture in the north and west, manufacturing in
the northeast, and timber and mining industries in the southeast.
Urban and industrial centers also have developed along Lake
Erie, the Ohio River, and the navigational canals and rivers that
join them. Surface water is the primary source of water for these
activities. Runoff in the state is determined largely by rainfall and
to a lesser degree by spring snowmelt. Earlier snowmelt would
result in higher streamflows in winter and spring. Lower stream-
flows and lake levels in the summer could reduce water availabil-
ity for municipalities and industries. The Ohio River and its major
tributaries, the Muskingum, Scioto, and Great Miami rivers, are
well developed with dams and reservoirs. Lower flows could
adversely affect important uses such as navigation and water
supply, although large storage reservoirs or changes in opera-
tions could moderate some impacts. Higher summer temperatures
and lower flows also could degrade water quality by concentrat-
ing pollutants. Drinking water quality, urban and industrial
discharges, and storm water overflows are important water
quality issues in Ohio.
Floods occur in Ohio nearly every year. In a warmer climate.
rainfall could be higher and storms could be more intense. Wetter
conditions would increase water availability, but could increase
flooding. Areas such as the Maumee and Blanchard river basins
and the lowlands south of Columbus are susceptible to flooding.
In the northern and western parts of the state, erosion of farmland
can be severe. Increased rains could exacerbate levels of pesti-
cides and fertilizers in runoff from agricultural lands and sedimen-
tation of navigation channels. It also could increase acid drainage
from mining activities in eastern and southeastern Ohio.
In a warmer climate, increased temperature and higher evapora-
tion could reduce inflows into the Great Lakes and lower lake
levels. Shorelines could be vulnerable to erosion damage from
wind and rain, but flood damage could be reduced. Harbors and
channels could require more dredging. Although lower water
levels in channels connecting the lakes could hamper shipping.
reduced ice cover would lengthen the shipping season. Warmer
temperatures could degrade lake water quality.
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
Corn Soybeans Hay
• AT = 8°F; Aprecip. = 3%
Corn Soybeans Hay
I AT = 9°F; Aprecip. = 13%
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 Ohio, production agriculture is a $4.4 billion annual industry.
two-thirds of which comes from crops. Very few of the farmed
acres are irrigated. The major crops in the state are corn, soy-
beans, and hay. Corn yields could fall by as much as 35% under
severe conditions where temperatures rise beyond the tolerance
levels of the crop and are combined with increased stress from
decreased soil moisture. Depending on how climate changes, hay
and pasture yields could fall by 16% or rise by 8%, and soybeans
yields could rise by 18% or fall by 3 3 %. Farmed acres could
remain fairly constant, or they could decrease by as much as 20%.
Nursery and horticulture crops are also important to Ohio
agriculture and could be affected by climate change. However.
these impacts have not been well studied, and because inputs
such as water are tightly managed for many of these crops, their
exposure to climate change may be limited.
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 oaks and pines, would prevail. Under these
Changes In Forest Cover
Current +10°F, +13% Precipitation
• Conifer Forest Savanna/Woodland
• Broadleaf Forest Grassland
Sources: VEMAP Participants (1995); Neilson (1995)
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 Ohio
could change little or decline by as much as 30-50%. Even if there
is no decline in forested area, the types of trees dominating those
forests and woodlands are likely to change. In a warmer climate.
forested areas could be increasingly dominated by pine and scrub
oaks, replacing many of the eastern hardwoods common through-
out Ohio forests. In areas where richer soils are prevalent or if
precipitation increases significantly, southern pines could
increase their range and density. In contrast, under drier condi-
tions or in areas with poorer soils (which are more common in
Ohio's forests), scrub oaks of little commercial value (e.g., post
oak and blackjack oak) could increase their range.
Ecosystems
Much of Ohio's landscape has been transformed by logging.
agricultural, urban, and industrial development, increasing the
importance of the few, high quality, natural communities that
remain today. The northern third of the state, which drains into
Lake Erie, contains plant communities ranging from deciduous
and hemlock forests to prairies, sand barrens, savannas, bogs.
fens, marshes, and sandy beaches. Oak savanna and wet prairie
habitats mark where eastern forests meet western prairie ecosys-
tems, and these are threatened communities. Less than 2% of the
original oak savannas in the Midwest exists today. This habitat
contains more than one-third of the rare plants and animals in
Ohio. Over 65 species of birds and many butterfly species nest
within the region, including the less than 20 nesting pairs of
endangered lark sparrow that survive in the state.
Ohio is in one of the nation's most highly industrialized
regions. It had already lost 90% of its wetlands between 1700
and 1980. Changes in climate could further threaten remaining
wetlands, particularly ecosystems within the Lake Erie drainage.
If the level of Lake Erie falls, the wetland habitats that depend
on inundation of freshwater from the lake would be adversely
affected. Warming could change the temperature structure of
lakes, availability of dissolved oxygen, and cycling of nutrients.
all of which will affect aquatic flora and fauna. If temperatures in
Lake Erie rise as projected, cold water refuges for certain fishes
may disappear and areas of warm water could increase, thus
altering the types and ranges offish species and communities.
Lower dissolved oxygen levels in Ohio ponds during warmer
years have reduced cool-water bottom habitat for northern pike.
summer weight, and development. Warmer water temperatures in
rivers and streams of the state could enhance invasion of white
perch, which exhibits higher winter survival of young during
warm winters.
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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