United States
Environmental Protection
Agency
Office of Policy, Planning
and Evaluation
(2111)
EPA 230-F-97-008g
September 1997
vxEPA Climate Change And Connecticut
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, 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. 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 since
the late 19th century. 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 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
Source: U.S. Department of State (1992)
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Global Temperature Changes (1861-1996)
03
0
I;-02
•0.4
•0.6
•0.8
f\
/x/Vv /\
/ \f
J
/\ A /
AA/W
f*
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
Fora 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
temperature could increase an average of 1,6-6.3°F by 2100, with
significant 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 J 0.000 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, average temperatures in Storrs,
Connecticut, have increased from 45.8°F (1892-1921 average)
to 48.2°F (1966-1995 average), and precipitation in some
locations has increased by 20%.
Over the next century, Connecticut's climate may change even
more. Based on projections given 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
Connecticut could increase about 4°F (with a range of 2-8°F) in
all seasons. Precipitation is projected to increase by 10-20%
(with a range of 0-40%), with slightly less change in spring and
summer and slightly more in winter.
The amount of precipitation on extreme wet (or snowy) days
most likely would increase, but changes in the lengths of wet
or dry spells are not clear. The frequency of extreme hot days
in summer is expected to increase along with the general
warming trend. It is not clear how severe storms such as hurri-
canes would change, although an increase in the frequency and/or
intensity of winter storms is possible.
Precipitation Trends From 1900 To Present
Trends/TOO years
+20%
+ 10%
+5%
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. Connecticut, with its irregular, intense heat
waves, may be especially susceptible.
In Hartford, one study projects that a 2°F warming could increase
heat-related deaths during a typical summer by about 20%, from
close to 40 heat-related deaths per summer to near 50 (although
increased air conditioning use may not have been fully accounted
for). Winter-related deaths are expected to change very little if
the temperature warms by 2°F. The elderly, particularly those
living alone, are at greatest risk.
There is concern that climate change could increase concentra-
tions 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 hydrocarbons emissions during hot weather. If a wanned
climate causes increased use of air conditioners, air pollutant
emissions from power plants also will increase.
A 4°F warming in New York City, with no other change in
weather or emissions, could increase concentrations of ozone, a
major component of smog, by 4%. Similar increases could be
expected in Connecticut. Currently, ground-level ozone concen-
trations exceed national ozone health standards throughout the
state. All of Connecticut is classified as a "serious" nonattainment
area for ozone. Ground-level ozone has been shown to aggravate
respiratory illnesses such as asthma, reduce existing lung func-
tion, and induce respiratory inflammation. In addition, ambient
ozone reduces crop yields and impairs ecosystem health.
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. Mosquitos flourish in some areas around
Connecticut. Some can carry malaria, while others can carry
Eastern equine encephalitis, which can be lethal or cause neuro-
Future Sea Level Rise At New London
110
100
90
80
70
60
50
40
30
20
10
0
5% Chance -
' 50% Chance—
95% Chance -
:,_ .
. . x
T J
2050 2100 2150 2200
Year
Source: EPA (1995)
logical damage. Lyme disease, which is carried by ticks, has
increased in Connecticut. If conditions become warmer and
wetter and thus support larger populations of mosquitos and ticks,
these diseases may be transmitted more widely.
In addition, warmer seas could contribute to the increased
intensity, duration, and extent of harmful algal blooms. These
blooms damage habitat and shellfish nurseries, can be toxic to
humans, and can carry bacteria like those causing cholera. Brown
algal tides and toxic algal blooms already are prevalent in the
Atlantic. Warmer ocean waters could increase their occurrence
and persistence.
Coastal Areas
Sea level rise could lead to flooding of low-lying property, loss
of coastal wetlands, erosion of beaches, saltwater contamination
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.
Along much of Connecticut's coast, sea level already is rising
8 inches per century, and it is likely to rise another 22 inches by
2100. Connecticut's coastline contains valuable residential
development and important wetlands ecosystems that would be
vulnerable to flooding from sea level rise. In particular,
Connecticut has extensive tidal flats and diverse nontidal fresh-
water marshes. Because Long Island Sound may reduce wave
action, some of these wetlands may be protected with a tempo-
rary buffer from erosion. Connecticut's freshwater marshes,
however, are likely to be harmed by saltwater intrusion.
Cumulative costs through 2100 to protect Connecticut's coastline
from a 20-inch sea level rise could be $0.5-$3 billion.
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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. In addition, more intense precipitation
could increase flooding. If streamflow and lake levels drop,
groundwater also could be reduced.
The Connecticut River is susceptible to changes in winter snow
accumulation, which would be reduced in a warmer climate.
Peak spring streamflows in the Connecticut River could occur
several weeks earlier if the climate were to warm about 4°F. The
Housatanic and Thames rivers could see similar but smaller
changes. Without increased precipitation, groundwater would
decrease in a wanner climate, which would reduce Connecticut's
aquifers.
Changes In Agricultural Yield And Production
Yield Production
Silage Hay
S3 AT = 7"F; Aprecip. = -1%
Silage ~ Hay
I AT = 10"F; Aprecip. = 12%
Source: Mendelsohn and Neumann (in press); McCarl (personal
communication)
Agriculture
The mix of crop and livestock production in a state is influenced
by climatic conditions and water availability. As climate warms,
production patterns will 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, and other
economic sectors.
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 substantially change modeling results. Analyses based on
changes, in average climate and which assume farmers effectively
adapt suggest that aggregate U.S. food production will not be
banned, although there may be significant regional changes.
In Connecticut, agriculture is a S500 million annual industry.
About one-twentieth of 1$ of total U.S. farm acres is in the state.
The principal crops are silage and hay, and very little of the
agricultural land is irrigated. Projections of changes in
Connecticut yields are mixed; they could range from little change
to decreases of almost 40%. Total acres farmed would remain
about the same, but farm income could decrease by about 50%.
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 extent, 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 would lead
to changes; trees that are better adapted to these conditions, such
as oaks and redwoods, would thrive. Under these conditions,
forests could become more dense. These changes could occur
during the lifetimes of today's children, particularly if they are
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
Connecticut could change little. However, a warmer climate
could change the character of Connecticut's forests. Maple-
dominated hardwood forests could give way to forests dominated
by oaks and conifers, species more tolerant of higher tempera-
tures. This change would diminish the brilliant autumn foliage as
the contribution of maples declines. Across the state, as much as
30-60% of the hardwood forests could be replaced by warmer
climate forests with a mix of pines and hardwoods.
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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