United States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007k
September 1998
<&EPA Climate Change And Maine
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 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
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 Lewiston.
Maine, has increased 3.4°F, and precipitation has decreased 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, Maine'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
Maine could increase by 4°F (with a range of 2-8°F), slightly less
in spring and fall and slightly more in summer and winter. Precipi-
tation is projected to show little change in spring, increase by
10% in summer and fall (with a range of 5-15%), and increase by
3 0% 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
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. Maine, with its occasional heat waves.
could be susceptible. In Boston, the nearest city in New England
for which heat wave projections have been made, one study
projects that a warming of 3°F could increase heat-related deaths
during a typical summer by 50-100% (although increased air
conditioning use may not have been fully accounted for). The
elderly, especially those living alone, are at greatest risk. This
study also shows that winter-related deaths will probably be
unaffected by climate change in northern New England.
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. In New
England, a 4°F warming, with no other change in weather or
emissions, could increase concentrations of ozone, a major
component of smog, by 4%. Currently, ground-level concentra-
tions exceed the national ozone health standard to a moderate
extent in Portland and in southern counties along the coast.
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. Respiratory and eye allergies increase in warm.
humid conditions.
Warmer temperatures could increase the incidence of Lyme
disease and other tick-borne diseases in Maine, because popula-
tions of ticks, and their rodent hosts, could increase under
warmer temperatures and increased vegetation.
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 Maine. These blooms damage habitat and shellfish nurseries
and can be toxic to humans.
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.
Maine has almost 3,500 miles of tidally influenced shoreline.
consisting of rocky peninsulas and harbors, pocket beaches.
islands, and complex estuaries. Because of the steep profile that
is characteristic of the Maine coastline and a lack of low-lying
land to be colonized by new marshes, there is likely to be a net
loss of marshes in Maine under accelerated sea level rise.
At Rockland, sea level already is rising by 3.9 inches per
century, and it is likely to rise another 14 inches by 2100. The
rocky substrate of Maine may slow erosion due to sea level rise.
and could complement efforts to protect the coastline. 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 Maine's
coastline from a 20-inch sea level rise by 2100 is estimated at
$200-$900 million. However, sand replenishment may not be cost-
effective for all coastal areas in the state and, therefore, some
savings could be possible.
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.
In Maine, production agriculture is a $500 million annual industry.
half of which comes from crops and the other half from livestock.
mainly poultry and dairy. Very few of the farmed acres are
irrigated. The major crops in the state are potatoes and hay.
Changes In Agricultural Yield And Production
100
Dryland Yield
Production
Hay Potatoes
• AT = 7°F; Aprecip. = -2%
Hay Potatoes
I AT = 11 °F; Aprecip. = 11%
Sources: Mendelsohn and Neumann (in press); McCarl
(personal communication)
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Climate change could reduce potato yields by 2-23%. Hay and
pasture yields could fall by as much as 39% as temperatures rise
beyond the tolerance level of the crop. Estimated changes in yield
vary, depending on whether land is irrigated. It is possible that
Maine farmers could alter their cropping practices to take
advantage of longer growing seasons and thus limit income
losses due to reductions in hay and potato yields.
Water Resources
A warmer climate would lead to an earlier spring snowmelt.
resulting in higher streamflows in winter and spring and lower
streamflows in summer and fall. Warmer summer temperatures and
longer summers could exacerbate water quality problems in rivers
such as the Androscoggin, where industry is significant and
pollution has traditionally been a problem. Warmer water tempera-
tures also reduce dissolved oxygen levels, adversely affecting
fish habitat, and lower summer streamflows could reduce the
ability of rivers to assimilate waste.
With more intense rainfall, increased flooding is possible.
particularly in steep headwater areas and along well-developed
floodplains. Greater and more intense rainfall could also increase
erosion in agricultural and timber-harvesting areas, resulting in
deposition of sediment in lakes and streams. Less rainfall,
particularly during the summer, could reduce streamflow, lake
levels, and groundwater levels. Streamflow reduction and warmer
temperatures would reduce habitat for cold water fish. This could
reduce water supplies in areas such as southwestern coastal
Maine, which is experiencing growing water demands due to
population growth and increased tourism.
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 substantially
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 oak, hickory, 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 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 Maine could change little
because of climate change, a warmer climate could change the
character of those forests. Maple-dominated hardwood forests
could give way to forests dominated by oaks and conifers.
species more tolerant of higher temperatures, especially along the
coast. This change would diminish the brilliant autumn foliage as
the number of maple trees declines. The spruce-fir forests in
Maine (and other New England states) are near the southern limit
of their extent. These forests are sensitive to climatic stresses and
have experienced significant declines in recent decades. Across
the state, as much as 35-60% of the hardwood forests could be
Changes In Forest Cover
Current +10°F, +13% Precipitation
| Conifer Forest
| Broadleaf Forest
Savanna/Woodland
Sources: VEMAP Participants (1995); Neilson (1995)
replaced by warmer-climate forests with a mix of pines and
hardwoods and, in some areas in the southeast, by grassland and
pasture. The extent and density of the spruce and fir forests at
higher altitudes, which support a large variety of songbirds, also
could be reduced by as much as 40-50%.
Ecosystems
The state of Maine is blanketed by northern hardwood/pine
forests in the south and a mosaic of hardwood/spruce and higher
elevation spruce-fir forests in the north and east. Maine's aquatic
resources include the St. John River, a section of which is the
longest free-flowing river segment in the northeastern United
States and home to over 30 species of rare plants, including the
endangered Furbish's lousewort. The state's long coastline
harbors estuarine barrier islands and marshes that provide habitat
for endangered species such as bald eagles, peregrine falcons.
piping plovers, and roseate terns.
The conifer forests found in higher elevations in the White
Mountains could be especially vulnerable to climate change.
Climate change could hasten the expansion of broad-leaved
forests into these pine forests, a transition that is already taking
place as a result of selective and intensive logging. The ranges
of spruce grouse, gray jays, boreal chickadees, snowshoe hares.
marten, and moose could be affected by reduced pine forests
and shifts in forest types. The already high threat of insect pest
outbreaks in the northern forest could be exacerbated by warm-
ing-induced changes in the timing of spring frosts. If precipitation
and runoff increase, the increased flooding of sensitive riparian
areas could destroy valuable and unique aquatic and riverine
habitats. Similarly, sensitive coastal ecosystems could be
damaged by increased tidal floodings associated with
increases in severe storms.
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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