United States
Environmental Protection
Agency
Office of Policy, Planning
and Evaluation
(2111)
EPA 230-F-97-008CC
September 1997
Climate Change And New Hampshire
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. Of these, 1995 was the
warmest year on record, suggesting the atmosphere has re-
bounded 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)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
±
r^ \ /
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 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 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 Hanover.
New Hampshire, has increased 2°F, and precipitation has
decreased by up to 20% in many parts of the state.
Over the next century, climate in New Hampshire 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 New Hampshire could increase by about
4°F (with a range of 2-9°F) in spring, and by about 5°F (with a
range of 2-10°F) in the other seasons. Precipitation is estimated
to show little change in spring, to increase by about 10% in
summer and fall, and to increase by 25-60% 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 would change, 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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Climate Change Impacts
Coastal Areas
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. New Hampshire, with its irregular heat
waves, could be susceptible.
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.
Currently, ground-level ozone concentrations exceed national
ozone health standards in the southern parts of New Hampshire.
Portsmouth is classified as a "serious" nonattainment area for
ozone. Ground-level ozone has been shown to aggravate respira-
tory illnesses such as asthma, reduce existing lung function, 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. Incidents of Lyme disease.
which is carried by ticks, have increased in the Northeast. If
conditions become warmer and wetter, tick populations could
increase in New Hampshire, thereby increasing the risk of
transmission of this disease.
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.
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.
New Hampshire has about 18 miles of seashore. New Hampshire's
coastline includes stretches of rocky shore, sand dunes and
beaches, productive estuaries, and dozens of islands. The Isles
of Shoals and the New Hampshire coast are favorable areas for
the American lobster.
At Seavey Island/Portsmouth, sea level already is rising by
7 inches per century, and it is likely to rise another 18 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, elevat-
ing 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 New Hampshire from a 20-inch sea level rise
by 2100 is estimated at $39-$304 million.
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.
The Connecticut River drains much of the state of New
Hampshire, and it forms the state's boundary with Vermont.
Several smaller rivers drain the remainder of the state, flowing
directly into the Atlantic Ocean. Winter snow accumulation and
spring melt strongly affect all the state's rivers. A warmer climate
would lead to earlier spring snowmelt, and result in higher
streamflows in winter and spring and lower streamflows in
summer and fall. Warmer summer temperatures and a longer
summer could exacerbate water quality problems such as algal
blooms in many of New Hampshire's lakes. With greater rainfall.
an increase in flooding is possible, while less rainfall could lower
groundwater levels because of reduced spring and summer
recharge. Thus, the water supply of some small municipalities
that depend on shallow aquifers could be reduced.
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.
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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 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 New Hampshire, agriculture is a $ 150 million annual industry.
three-fifths of which comes from crops. Very little of the crop
acreage is irrigated. The major crops in the state are silage and
hay. Climate change could change crop yields and production
very little or by as much as 39%.
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 would 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
Changes In Forest Cover
Changes In Agricultural Yield And Production
Irrigated Yield Production
Current
+ 10°F,
+ 13% Precipitation
• Conifer Forest
• Broadleaf Forest
Savanna/Woodland
Source: VEMAP Participants (1995);
Neilson (1995)
Silage Hay
• AT = 7°F; Aprecip. = -2%
Silage Hay
AT =11°F; Aprecip. = 11%
Source: Mendelsohn and Neumann (in press); McCarl (personal
communication)
lifetimes of today's children, particularly if change is accel-
erated 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 New Hampshire 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 25-50% of
the hardwood forests could be replaced by warmer-climate
forests with a mix of pines and hardwoods. The extent and
density of the spruce and fir forests at higher altitudes, which
support a large variety of songbirds, also could be reduced.
Ecosystems
The 6,200 acres of salt marshes along the coast and around the
Great Bay estuary of New Hampshire are a critical habitat for
some wildlife species such as sharp-tailed sparrows. The salt
marshes are also a major feeding ground for snowy egrets and
great blue herons. These regions could be affected adversely
by changes in runoff and sea level.
Climate change could also affect the Lake Umbagog National
Wildlife Refuge, which includes the 8,700 acre lake, its associ-
ated uplands, and freshwater marshes in northern New
Hampshire. This unique habitat supports many migratory
wildlife species, including the bald eagle and the endangered
peregrine falcon. For the common loon and osprey, this refuge
is considered to be the best breeding habitat in New Hampshire.
In mountain areas, alpine ecosystems could be vulnerable to
climate change. Warmer temperatures and changes in rainfall
could reduce habitat for cold-water fishes and aquatic insects.
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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