United States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007V
September 1998
©EPA Climate Change And Rhode Island
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 outbreaks)
could increase.
Local Climate Changes
Over the last century, the average temperature in Providence.
Rhode Island, has increased 3.3°F, and precipitation has in-
creased 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, Rhode Island's climate may change
even more. For example, based on projections made by the
Intergovernmental Panel on Climate Change and results from the
United Kingdom Hadley Centre climate model (HadCM2), a model
that accounts for both greenhouse gases and aerosols, by 2100
temperatures in Rhode Island could increase by 4°F (with a range
of 1-8°F) in winter and spring and by 5°F (with a range of 2-10°F)
in summer and fall. Precipitation is projected to increase by 10%
in spring and summer (with a range of 5-15%), 15% infall (with a
range of 5-30%), and 25% in winter (with a range of 10-50%).
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 amount of precipitation on extreme
wet or snowy days in winter 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 the severity
of storms such as hurricanes might be affected, an increase in
the frequency and intensity of winter storms 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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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. Rhode Island, with its irregular, intense
heat waves, could be susceptible. One study projects that a
warming of 3-4°F could increase heat-related deaths during a
typical summer in Providence by 50% from the current 50 to near
75 (although increased air conditioning use may not have been
fully accounted for). This study also shows that winter-related
deaths in Providence could rise by 25% given a 2°F warming.
However, the exact reasons for this increase are unknown. The
elderly, especially 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. Based
on projections for New York City, a 4°F warming could increase
concentrations of ozone, a major component of smog, by 4%.
Currently, ground-level concentrations exceed the national
ozone health standard throughout the state. All of Rhode Island
is classified as a serious nonattainment area for ozone. 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 hydro-
carbon emissions 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.
Warmer temperatures could increase the incidence of Lyme
disease and other tick-borne diseases in Rhode Island, because
populations of ticks, and their rodent hosts, could increase under
warmer temperatures and increased vegetation. Respiratory and
eye allergies increase in warm, humid conditions.
Warmer winters, warmer temperatures, and heavy precipitation
also can increase harmful algal blooms, that is, red tides; reduce
water quality; and increase outbreaks of cryptosporidiosis and
giardia. In addition, warmer seas could contribute to the intensity.
duration, and extent of harmful algal blooms in the coastal waters
of Rhode Island. These blooms damage habitat and shellfish
nurseries and can be toxic to humans.
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 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.
Rhode Island is endowed with over 400 miles of densely
populated, tidally influenced shoreline, consisting of both sandy
and gravel barrier beaches, and rocky cliffs. Block Island and
Future Sea Level Rise At Watch Hill
90
70
50
30
?0
10
0
- • 5% Chance
- • 50% Chance
_ . 90% Chance
T
I ]
I
-
2050
Source: EPA (1995)
2100 2150
Year
2200
Narragansett Bay contain relatively undisturbed salt marshes.
tidal flats, rocky shores, and small islands. The beaches along
the Rhode Island coast are highly developed and heavily used
by hundreds of thousands residents and out-of-state visitors
each year. These beaches have suffered severe damage during
hurricanes and storm surges. In general, erosion is most severe at
the barrier beaches on the south shore of Rhode Island and bluff
areas on Block Island; these areas are likely to erode most if sea
level rises. The northern shore of Narragansett Bay, including
Cranston, Providence, and Pawtucket, is heavily armored with
seawalls and other erosion control devices.
At Watch Hill, sea level already is rising by 2 inches per century.
and it is likely to rise another 12.4 inches by 2100. Possible
responses 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 Rhode
Island's coastline from a 20-inch sea level rise by 2100 is esti-
mated at $90-$530 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
The principal rivers in Rhode Island are the Blackstone, the
Pawtuxet, and the Pawcatuch, which drain toward Narragansett
Bay and Block Island Sound. Water resources in Rhode Island are
currently abundant and well developed. Most of the freshwater
used in the state comes from reservoirs, lakes, and rivers. Sciture
Reservoir, in southern Providence County, serves nearly one-half
of the state's population. Winter snow accumulation and spring
snowmelt strongly affect the state's rivers. A warmer climate
would lead to an earlier snowmelt, resulting in higher streamflows
in winter and spring. Without increases in precipitation, higher
temperatures and increased evaporation would lower
streamflows, lake levels, and groundwater levels in the
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summer and fall. This could aggravate water supply problems.
particularly in the southern part of the state, where water demand
is highest. Groundwater sources, recently developed to meet
growing demand in the state, also could be reduced by lower
spring and summer recharge. Lower summer streamflows and
warmer temperatures also could increase water quality problems
by concentrating pollutant levels, particularly in parts of rivers
where effluent from municipal wastewater treatment facilities
and industries is dumped. Increases in rainfall could mitigate
these effects. Higher rainfall, however, could contribute to
localized flooding, increased levels of pesticides and fertilizers
from agricultural runoff, and increased pollution from urban
runoff. During periods of high flow, the water quality in northern
Narragansett Bay is particularly susceptible to pollution from
sewer overflows and stormwater runoff from the highly urbanized
area around Providence.
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 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.
Changes In Agricultural Yield And Production
Dryland Yield Production
10
0
-10
-20
-30
-40
-50
-70
-90
Silage Hay Potatoes
• AT = 7°F; Aprecip. =-2%
Silage Hay Potatoes
AT =10°F; Aprecip. = 11%
Sources: Mendelsohn and Neumann (in press); McCarl
(personal communication)
In Rhode Island, production agriculture is a $78 million annual
industry, three-fourths of which comes from crops. Very few of
the farmed acres are irrigated. The major crops in the state are
silage, potatoes, and hay. Climate change could reduce potato
yields by 30-66%. Silage, hay, and pasture yields could fall as
much as 39% as temperatures rise beyond the tolerance level of
the crop. Farmed acres may remain constant or could fall by as
much as 14%. Estimated changes in yield vary, depending on
whether land is irrigated.
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 and density 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
these conditions, such as oaks and pines, would thrive. 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
themselves be worsened by a warmer and drier climate.
Although the extent of forested areas in Rhode Island could
change little because of climate change, a warmer climate could
change the character of those forests. Maple-dominated hard-
wood forests could give way to forests dominated by oaks and
conifers, species more tolerant of higher temperatures. 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.
Ecosystems
The smallest state in the country, Rhode Island is almost entirely
a coastal area. Its marshes, estuaries, and salt ponds are critical
habitats for waterfowl and other migratory birds, as well as for
many terrestrial animals. The many streams and rivers that enter
Narragansett Bay provide important spawning habitat for shad.
herring, and Atlantic salmon. Barrier reef islands such as Block
Island in Narragansett Bay are important as refuges for a number
of rare and endangered species, including the grasshopper
sparrow, savannah sparrow, northern harrier hawk, and American
burying beetle. These islands are also key stopover points for
migratory songbirds.
The fragile coastal ecosystems of Rhode Island are particularly
susceptible to destruction as sea level rises and barrier reef
islands are inundated, and if the frequency and severity of storms
increase. Such losses would reduce coastal habitat that supports
diverse sea life and migratory waterfowl.
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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