—
United States
Environmental Protect!
Agency
-Office of Policy
,(2131)
-EPA 236-Fy8-O
September 1998
Climate Change^And North Dakota
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
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.
A
Some solar radiation
is reflected by the
earth and the
atmosphere
Solar
radiation
passes
through
the clear
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 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
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
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Global Temperature Changes (1861-1996)
-1
^ ^ ^ ^ ^N ^N\<^ N# ^ >& N# >& & N#
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 near Bismarck,
North Dakota, has increased 1.3°F, and precipitation has
decreased by up to 10% in many parts of the state, except in
the southeastern part of the state where precipitation has
risen slightly. These past trends may or may not continue into
the future.
Over the next century, climate in North Dakota 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 North Dakota could increase by 3°F in
summer (with a range of 1-5°F) and 4°F in the other seasons
(with a range of 2-7°F). Precipitation is estimated to increase by
5% in spring (with a range of 0-10%), 10% in summer (with a
range of 5-20%), 15% in fall (with a range of 5-25%), and 25%
(with a range of 10-40%) in winter. 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. It is not clear how
the severity of storms might be affected, although 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. These effects have been studied only for
populations living in urban areas; however, even those in rural
areas may be susceptible. North Dakota lacks large cities, which
are most sensitive to heat waves; however, Minneapolis will
experience similar changes in climate and could indicate how
populations in North Dakota cities might be affected. One study
estimates that in Minneapolis a summer warming of 5°F could
increase heat-related deaths by threefold (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 in North Dakota
could be little changed.
Upper and lower respiratory allergies are influenced by humidity.
A 2°F warming and wetter conditions could increase respiratory
allergies.
Warming and other climate changes could expand the habitat
and infectivity of disease-carrying insects. Infected individuals
can bring malaria to places where it does not occur naturally.
Also, some mosquitoes in North Dakota can carry malaria, and
others can carry western equine encephalitis, which can be lethal
or cause neurological damage. If conditions become warmer and
wetter, mosquito populations could increase, thus increasing the
risk of transmission if these diseases are introduced into the area.
Warmer temperatures could increase the incidence of Lyme
disease and other tick-borne diseases in North Dakota, because
populations of ticks, and their rodent hosts, could increase under
warmer temperatures and increased vegetation. Increased runoff
from heavy rainfall could increase water-borne diseases such as
giardia, cryptosporidia, and viral and bacterial gastroenteritides.
Developed countries such as the United States should be able to
minimize the impacts of these diseases through existing disease
prevention and control methods.
Water Resources
Major river basins in North Dakota include the Missouri, which
drains the west-central part of the state, and those of the Souris
River and Red River of the North, which drain northward into
Canada. These surface waters are the primary source of water in
the state, and agriculture is the dominant user of water. The
mainstem of the Missouri and the lower Red River of the North
are dependable sources, but other rivers are not reliable because
of low flows and variable water quality. Runoff in North Dakota
is influenced largely by spring-summer rainfall and spring
snowmelt. Warmer temperatures would lead to earlier spring
snowmelt, resulting in higher streamflows in winter and spring. In
the summer, without large increases in precipitation, higher
temperatures and increased evaporation would lower streamflows
and lake levels. Although large storage reservoirs such as Lakes
Sakakawea and Oahe might be able to moderate these impacts,
the numerous smaller reservoirs throughout the state could be
adversely impacted. Less water would be available to support
important uses such as irrigation, hydropower production,
industrial and mining operations, municipal water supplies,
recreation, and fish and wildlife habitats. Evaporation often
exceeds precipitation in this semiarid state, and many small rivers
and streams run dry in the summer. Warmer, drier summers would
exacerbate this situation. Groundwater levels also could be
reduced by lower spring and summer recharge. Groundwater is an
important source of water in rural areas, and a supplementary
source for urban water supplies and for irrigation in areas distant
from large rivers. Higher summer temperatures and lower flows
also could degrade water quality by concentrating pollutants and
reducing the capacity of streams to assimilate wastes from
industrial, municipal, and livestock wintering areas. Wetlands and
prairie potholes, which provide important waterfowl habitat, also
would be impaired by declining water levels.
More rain could alleviate some of these impacts, but also could
increase flooding. Floods are common along Red River of the
North and the Souris River, and can be as severe as they were in
1997. The valley of the Red River of the North is the most
populous area in the state and the most intensively farmed. The
low gradient of the river renders it particularly susceptible to
urban and agricultural flood damage. Under wet conditions,
rising water levels in Devils Lake in northeastern Dakota can
cause flooding in nearby areas. Increased rainfall and streamflow
also could increase erosion and exacerbate levels of pollution in
runoff. This could exacerbate water quality problems associated
with fertilizer runoff from agricultural lands and leachate from
mining and oil and gas operations.
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.
Changes In Agricultural Yield And Production
Dryland Yield Production
Wheat Barley Hay Wheat Barley Hay
• AT = 8°F; Aprecip. = 7% HI AT = 8°F; Aprecip. = 17%
Sources: Mendelsohn and Neumann (in press); McCarl (personal
communication)
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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 North Dakota, production agriculture is a $3 billion annual
industry, two-thirds of which comes from crops. Very few of the
farmed acres are irrigated. The major crops in the state are wheat,
barley, and hay. Climate change could marginally increase yields
of all of these crops, with wheat rising by 2-18% and the other
crops by 2-4%. Farmed acres could remain fairly constant or
could decrease by as much as 28%.
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
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 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.
With changes in climate, the extent of the few forested areas in
North Dakota could change little or decline almost entirely. The
uncertainties depend on many factors, including whether soils
become drier and, if so, how much drier. Hotter, drier weather
could increase the frequency and intensity of wildfires, decreas-
ing the range and density of ponderosa pines and northern aspen-
birch forests. Grasslands and savanna eventually could replace
many of the forests and riparian woodlands in North Dakota.
Increases in rainfall could, however, reduce the severity of these
changes. These changes would significantly affect the character
of forests and woodlands in North Dakota.
Changes In Forest Cover
Current +10°F, +13% Precipitation
Ecosystems
In North Dakota, eastern forests are found along with tallgrass,
midgrass, and shortgrass prairies. An ecological transition zone,
the state boasts Great Plains riverine forests, hardwood ravines,
and a range of aquatic habitats. The Prairie Pothole Region, so
crucial for waterfowl populations, covers large portions of the
eastern and central parts of the state. More than half of North
America's waterfowl production occurs in the Prairie Pothole
Region. Many notable wildlife refuges are home to an incredible
wealth of wildlife species. At Des Lacs National Wildlife Refuge,
flocks of 250,000 snow geese are sometimes present. Up to
200,000 franklins and ring-billed gulls visit Tewaukon National
Wildlife Refuge. Drainage of wetlands, agricultural encroach-
ment, and increased fragmentation of native prairie are suspected
in the recent declines of wetland and open grassland bird species.
Since the 1970s, mallard, blue-winged teals, and northern pintails
have been close to their lowest recorded populations. At same
time, fire suppression and less grazing have resulted in encroach-
ment by woody vegetation, and species associated with woody
vegetation have increased dramatically. Increased nest predation
by red fox, striped skunk,land raccoon has reduced nesting
success of five species of ducks to levels that appear to be too
low to support stable numbers of breeding ducks in the Prairie
Pothole Region. Climate change could further stress and endan-
ger many of these ecosystems.
The state's wildlife refuges and prairie pothole systems appear to
be especially sensitive to changes in precipitation and tempera-
ture. Sixty percent of the annual variation in the number of these
wetlands can be explained by year-to-year changes in temperature
and precipitation. Smaller wetlands may be particularly vulner-
able. Model projections show that warmer annual temperatures
could result in reduced open water and greater vegetation cover,
independent of precipitation changes. Rising temperatures, if
continued for several years, could decrease breeding bird density
and diversity in this critically important waterfowl habitat. Major
threats to other ecosystems include habitat loss and species
extinction, increased fire frequency, and increased vulnerability
to invasive plant and insect species. Many species have already
suffered significant declines because of loss of habitat, including
bison, white tailed prairie dog, Arkansas River shiner, speckled
chub, and numerous grassland and migratory birds. Species of the
upland prairie may face additional problems in a changing
climate. Under projected climate changes, all 23 grassland bird
species could move north into regions that at the moment are
mostly forest and are not expected to convert to grassland within
the tune frame of the projected warming. Hence, the size and
fragmented nature of the existing grassland patches in the north
would place an additional burden on bird populations.
Conifer Forest
Broadleaf Forest
Savanna/Woodland
Shrub/Woodland
Grassland
Sources: VEMAP Participants (1995); Neilson (1995)
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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