United States
Environmental Protection
Agency
Office of Policy, Planning
and Evaluation
(2111)
EPA 230-F-97-008U
September 1997
Climate Change And Massachusetts
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.
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
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.
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^ \ /
Year
Source: IPCC (1995), updated
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. Scientists are reasonably confident 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 Amherst.
Massachusetts, has increased 2°F, and precipitation has increased
by up to 20% in many parts of the state.
Over the next century, climate in Massachusetts 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's climate model (HadCM2).
a model that accounts for both greenhouse gases and aerosols.
by 2100 temperatures in Massachusetts could increase by about
4°F (with a range of 1-8°F) in winter and spring and about 5°F
(with a range of 2-10°F) in summer and fall. Precipitation is
estimated to increase by about 10% in spring and summer, 15%
in fall, and 20-60% in winter. Other climate models may show
different results. 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 severe
storms such as hurricanes would change, an increase in the
frequency and intensity of winter storms is possible.
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.
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. Massachusetts, with its irregular, intense
heatwaves, could be especially susceptible.
In Boston, one study projects that by 2050 heat-related deaths
during a typical summer could increase 50%, from close to 100
heat-related deaths per summer to over 150 (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 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 occur
in Massachusetts. Currently, ground-level ozone concentrations
exceed national ozone health standards throughout the state. All
of Massachusetts 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 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 some areas around
Massachusetts. Some can carry malaria, while others can carry
Eastern equine encephalitis, which can be lethal or cause neuro-
logical damage. Incidents of Lyme disease, which is carried by
ticks, have increased in the Northeast. If conditions become
warmer and wetter, mosquito and tick populations could increase.
thereby increasing the risk of transmission of these diseases.
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.
The coast of Massachusetts is an important resource with over
1,500 miles of shoreline. Massachusetts' coastline includes
stretches of rocky shore, barrier beaches, productive estuaries.
fragile salt marshes, tidal flats, and dozens of islands. Barrier
beaches, salt marshes, and other wetland resource areas buffer
the coast from storms, waves, and flooding.
At Boston, sea level already is rising by 11 inches per century.
and it is likely to rise another 22 inches by 2100. Rising sea
levels are taking a toll on Massachusetts' coastal upland. Each
year, an average of 65 acres of upland is submerged by a combi-
nation of rising seas and subsiding land. Much of this loss occurs
along the south-facing coast between Rhode Island and the outer
shore of Cape Cod, including the islands of Nantucket and
Martha's Vineyard. Coastal land that has been lost because of
erosion by storm waves or wetland erosion is not included in the
estimate of annual average land lost from submersion.
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 the
coast of Massachusetts from a 20-inch sea level rise by 2100 is
estimated at $490 million to $2.6 billion.
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.
Future Sea Level Rise
At Woods Hole, Cape Cod
I£U
110
100
90
20
n
5% Chance — i—
50% Chance — —
95% Chance —I—
~ ~
2100
Source: EPA (1995)
2200
Year
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Western Massachusetts drains to the Connecticut River, and the
eastern parts of the state drain directly to the Atlantic Ocean.
Relatively little of the flow of the Connecticut River originates in
Massachusetts, but it is the source of much of the water supply
for the Boston metropolitan area. The flow of the Connecticut is
strongly affected by winter snow accumulation and runoff from
Vermont and New Hampshire. A warmer climate would lead to
earlier spring snowmelt, resulting in higher streamflows in winter
and spring and lower streamflows in summer and fall. However.
warmer summer temperatures could increase water quality
problems because of increased evaporation (which concentrates
pollutant levels) and more favorable conditions for algae and
other water organisms. Increased rainfall could mitigate these
effects, but it also could contribute to localized flooding.
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
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 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 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 Massachusetts, agriculture is a $500 million annual industry.
three-fourths of which comes from crops. Very little of the crop
acreage is irrigated. The major crops in the state are silage, hay.
and potatoes. Climate change could change crop yields little or
Changes In Agricultural Yield And Production
Irrigated Yield Production
Silage Hay Potatoes
• AT = 7°F; Aprecip. = -2%
Silage Hay Potatoes
AT = 10°F; Aprecip. = 13%
Source: Mendelsohn and Neumann (in press); McCarl (personal
communication)
cause them to fall by as much as 45%, leading to changes in acres
farmed and production. For example, potato yields could de-
crease while production rises because of an increase in potato
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
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 conditions, such
as oaks and 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 acceler-
ated 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 Massachusetts 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 number
of maple trees 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 coastal beaches and tidal marshes of Massachusetts are
especially sensitive to the effects of sea level rise and changes
in river flows. Sea level rise could inundate coastal wetlands.
destroying habitat for commercial and game species as well as
migratory birds and other wildlife. Barrier beach island refuges
such as the Monomoy National Wildlife Refuge south of Cape
Cod and the Parker River National Wildlife Refuge in northeast-
ern Massachusetts could be threatened or lost. These refuges
provide important habitat for migratory birds, including the
threatened piping plover and the endangered roseate tern. Harbor
and gray seals, which use beaches as refuge in the winter, also
could lose habitat if sea levels rise.
Forests and woodlands support much of the wildlife in the state.
Climate change could result in changes in these ecosystems.
Fragmented land use patterns could impede migration of some
plant species, resulting in loss of some native plants and increases
in non-native plants. Changes in rainfall and runoff could change
sediment levels in streams and wetlands, thus affecting fish and
aquatic habitats.
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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