United States
                           Environmental Protection
Office of Policy, Planning
and Evaluation
                                                                        EPA 230-F-97-008V
                                                                        September 1997
       <&EPA       Climate  Change And  Michigan
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 60F. 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
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
     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 0.6-1.2F since
   the late 19th century. 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 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

     Global Temperature Changes (1861-1996)

    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 1.6-6.3F by 2100, with signi-
ficant 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 Ann Arbor.
Michigan, has increased from 46.6F (1876-1905 average) to
47.7F (1962-1991  average), and precipitation in some locations
in the state has increased by up to 20%.

Over the next century, Michigan's climate may change even
more. Based on projections given by the Intergovernmental Panel
on Climate Change  and results from the United Kingdom Hadley
Centre's climate model (HadCM2), a model that has accounted
for both greenhouse gases and aerosols, it is projected that by
2100, temperatures  in Michigan could increase by about 4F in
all seasons (with a range  of 2-8F). Precipitation is projected to
increase by 5-15% in winter, spring, and fall, and by around 20%
(with a range of 10-40%) in summer.

The amount of precipitation on extreme wet days in summer most
likely would increase. The frequency of extreme hot days in
summer is expected to increase along with the general warming
trend. It is not clear how severe storms would change.
     Precipitation Trends From 1900 To Present
                                       Trends/100 years
                                           -20% O
Source: Karl et al. (1996)

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.
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. Michigan, with its irregular, intense heat
waves, seems somewhat susceptible.

In Detroit, one study projects that a 3F warming could increase
heat-related deaths during a typical summer from 110 to possibly
over 200 (although increased air conditioning use may not have
been fully accounted for). If the warming is 5F, heat-related
deaths could be about 250 during a typical summer. Winter-
related deaths could drop from 35 in Detroit per winter to about
20 if winter temperatures warm by 3-5F. The elderly, particularly
those living alone, are at greatest risk.

There is concern that climate change could increase concentra-
tions 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 hydrocarbons emissions during hot weather. If a warmed
climate causes increased use of air conditioners, air pollutant
emissions from power plants also will increase.

A 4F warming in the Midwest, with no other change in weather
or emissions, could increase concentrations of ground-level
ozone, a major component of smog, by as much as 8%. Perhaps
more important, however, is that the area not meeting national
health standards for ozone could almost triple. Currently.
Muskegon is the only county in Michigan that does not attain the
National Ambient Air Quality Standards for ozone. Ground-level
ozone has been shown to aggravate existing respiratory illnesses
such as asthma, reduce lung function, 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, increasing the potential for
transmission of diseases such as malaria and dengue ("break
               Changes In Forest Cover
            Current             +10F, +13% Precipitation
       Conifer Forest
       Broadleaf Forest
                                                               Source: VEMAP Participants (1995);  Neilson (1995)
bone") fever. Mosquitoes flourish in Michigan, and some carry
St. Louis encephalitis. The mosquitoes that carry this disease
could increase with climate change. Also, the mosquitoes that
carry yellow fever, dengue fever, Eastern equine encephalitis, and
La Crosse encephalitis recently have spread as far north as
Chicago. Global warming could shift the region where these
mosquitoes breed and overwinter farther north. If conditions
become warmer and wetter, mosquito populations could increase.
thereby increasing the risk of transmission of these diseases.


Trees and forests are adapted to specific climate conditions, and
as climate warms, forests will change. These changes could
include changes in species, geographic extent, and health and
productivity. If conditions also become drier,  the current range
and density of forests could be reduced and replaced by grass-
lands and pasture. Even a warmer and wetter climate would lead
to changes; trees that  are better adapted to these conditions, such
as oaks and redwoods, would thrive. Under these conditions.
forests could become  more dense. These changes could occur
during the lifetimes of today's children, particularly  if they are
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 forested areas in Michigan
could change  little or  decline by as much as 50-70%. The
uncertainties depend on many factors, including whether soil
becomes drier and, if  so, by how much drier. Hotter, drier
weather could increase the frequency and intensity of wildfires.
The mixed aspen, birch, beech, maple, and pine forests found in
the north could be replaced over time by a combination of
grasslands, savannah, and hardwood forests of oak, elm, and ash.
The predominant hardwood forests in the south could give way to
pine and oak forests. These changes  could affect the character of
Michigan forests and  the activities that depend on them.

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. In addition, more intense precipitation
could increase flooding. If streamflow and lake levels drop.
groundwater also could be reduced.

All but a fraction of Michigan streams drain to one of the three
upper Great Lakes (Superior, Michigan, and Huron). In a warmer
climate, the seasonal flow in the state's streams and rivers would
peak earlier. Because evaporation would increase in a warmer
climate, summer streamflows probably would decrease, which
could have important implications for stream  health.

Shorter ice-cover seasons and increased lake evaporation could
have major effects on the Great Lakes. Fresh water flowing into
the Great Lakes could decrease by 20% with a 4F warming.
potentially reducing lake levels by a foot or more. Flood damage
could be reduced, but shorelines could be  more susceptible to
erosion damage from wind and rain. Reduced fresh water in the
Great Lakes could impede shipping to and from Michigan ports.
primarily because  of lower water levels in the shipping channels
connecting the lower Great Lakes.

The mix of crop and livestock production in a state is influenced
by climatic conditions and water availability. As climate warms.
production patterns will 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, and other
economic 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 substantially change modeling results. Analyses based on
changes in average climate and which assume farmers effectively
adapt suggest that aggregate U.S. food production will not be
harmed, although there may be significant regional changes.
   Changes In Agricultural Yield And Production

                 Yield                     Production
         Corn Soybeans  Hay

            DT = 8F; Dprecip. = 1 %
 Corn Soybeans  Hay

I DT= 10F; Dprecip. = 16%
Source: Mendelsohn and Neumann (in press); McCarl (personal
In Michigan, agriculture is about a $3 billion annual industry.
50% of which comes from livestock. The principal crops are
corn, soybeans, and hay. About 4% of the state's farm acres is
irrigated. If climate warms, corn yields are projected to remain
unchanged or could decrease by up to 34%.  Soybean yields could
either decrease or increase, and hay yields could remain un-
changed or decrease by 17%. Acres farmed could remain
unchanged, and farm income could decrease by 10-40%. Irrigated
acreage could increase. This could further increase the demands
for available water, and water quality could be further degraded.


A rise in water temperatures in the Great Lakes would reduce the
size of favorable habitat for trout, whitefish, and other coldwater
fish species. If groundwater-fed streams experienced an increase
in temperature, brook trout could lose all their habitat, and brown
and rainbow trout could lose most of their habitat. Warm water
fish, both native and introduced, could experience longer growing
seasons and flourish in a warmer climate.

The well-known Kirtland's warbler breeds only in the jack pine
forests of northern lower Michigan. Because the jack pines may
not survive in Michigan if the climate warms, the existence of the
Kirtland's warbler could be threatened.
                                                              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.