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What Climate Change

lllinois's climate is changing. Most of the state has
warmed by about one degree (F) in the last century.
Floods are becoming more frequent, and ice cover on
the Great Lakes is forming later or melting sooner. In the
coming decades, the state will have more extremely hot
days, which may harm public health in urban areas and
corn harvests in rural areas.
Our climate is changing because the earth is warming.
People have increased the amount of carbon dioxide
in the air by 40 percent since the late 1700s. Other
heat-trapping greenhouse gases are also increasing.
These gases have warmed the surface and lower
atmosphere of our planet about one degree during the
last 50 years. Evaporation increases as the atmosphere
warms, which increases humidity, average rainfall, and
the frequency of heavy rainstorms in many places—but
contributes to drought in others.
Greenhouse gases are also changing the world's oceans
and ice cover. Carbon dioxide reacts with water to form
carbonic acid, so the oceans are becoming more acidic.
The surface of the ocean has also warmed about one
degree during the last 80 years. Although warmer tem-
peratures cause sea level to rise, the impact on water
levels in the Great Lakes is not yet known. Warmer air
also melts ice and snow earlier in spring.
Temperature change (°F):
-1 -0,5 0 0.5 1 1.5 2 2.5 3 B.5
Rising temperatures in the last century. Northern Illinois has
warmed more than southern Illinois. Source: EPA, Climate
Change Indicators in the United States.
The Mississippi River flooding at the Quincy Lock and Dam 21 in Quincy in
June 2008. The lock is submerged in the foreground and the dam is visible
to the left. Credit: USGS, Advanced Hydrological Prediction Service.
Heavy Precipitation and Flooding
Changing climate is likely to increase the frequency of floods in Illinois,
Over the last half century, average annual precipitation in most of the
Midwest has increased by 5 to 10 percent. But rainfall during the four
wettest days of the year has increased about 35 percent, and the
amount of water flowing in most streams during the worst flood of the
year has increased by more than 20 percent. During the next century,
spring rainfall and average precipitation are likely to increase, and
severe rainstorms are likely to intensify. Each of these factors will
tend to further increase the risk of flooding.
Illinois, Ohio, and Mississippi Rivers
Flooding occasionally threatens both navigation and riverfront
communities, and greater river flows could increase these threats.
In 2011, a combination of heavy rainfall and melting snow caused
a flood that closed the Ohio and Mississippi rivers to navigation and
prompted evacuation of Cairo due to concerns that its flood protection
levees might fail. To protect Cairo, the U.S. Army Corps of Engineers
opened the Birds Point-New Madrid Floodway, which lowered the
Mississippi River by flooding more than 100,000 acres of farmland in
Missouri. The flood caused $360 million of damage to infrastructure,
property, and agricultural yields upstream.

Although springtime in Illinois is likely to be wetter, summer
droughts are likely to be more severe. Higher evaporation and
lower summer rainfall are likely to reduce river flows. The
drought of 2012 narrowed navigation channels, forced lock
closures, and caused dozens of barges to run aground along
the Illinois shoreline of the Mississippi River, all of which
delayed shipping. The Corps of Engineers estimates that the
drought's impact on navigation cost the region more than $275
million. Both floods and drought can cause problems for the
Illinois Waterway, which carries 25 million tons of cargo per
year between Chicago and the Mississippi River.
One advantage of climate change is that warmer winters reduce
the number of days that ice prevents navigation.
Great Lakes
The ice-free season along the Great Lakes is also becoming
longer. Between 1994 and 2011, reduced ice cover lengthened
the shipping season on the lakes by eight days. The Great Lakes
are likely to warm another 3° to 7°F in the next 70 years, which
will further extend the shipping season.
In Lake Michigan, changing climate is likely to harm water
quality. Warmer water tends to cause more algal blooms,
which can be unsightly, harm fish, and degrade water quality.
Severe storms also increase the amount of pollutants that run
off from land to water, so the risk of algal blooms will be greater
if storms become more severe. Increasingly severe rainstorms
could also cause sewers to overflow into the lake more often,
threatening beach safety and drinking water supplies.
Changing climate will have both beneficial and harmful effects
on farming. Longer frost-free growing seasons and higher
concentrations of atmospheric carbon dioxide would increase
yields for some crops during an average year. But increasingly
hot summers are likely to reduce yields of corn and possibly
soybeans. Seventy years from now, southern Illinois is likely to
have 15 to 20 more days with temperatures above 95°F than it
has today. More severe droughts or floods would also hurt crop
Parched and stunted corn
during a summer drought in
Illinois. Credit: USGS.
Air Pollution and Human Health
Rising temperatures can harm air quality and amplify existing
threats to human health. Warmer weather can increase the
production of ground-level ozone, a pollutant that causes lung
and heart problems. Ozone also harms plants. In rural Illinois,
ozone ievels are high enough to significantly reduce yields of
soybeans and winter wheat. U.S. EPA and the Illinois EPA have
been working to reduce ozone concentrations. As the climate
changes, continued progress toward clean air will become more
Hot days can be unhealthy, even dangerous. High air tempera-
tures can cause heat stroke and dehydration, and affect people's
cardiovascular and nervous systems. Northern cities like
Chicago are vulnerable to heat waves, because many houses
and apartments lack air conditioning, and urban areas are
typically warmer than their rural surroundings. Heat waves kill
approximately 50 people per year in Chicago. In the next
70 years, climate change is likely to substantially increase
heat-related deaths. Certain people are especially vulnerable,
including children, the elderly, the sick, and the poor.
The sources of information about climate and the impacts of climate change In this publication are: the national climate assessments by the U.S. Global Change Research
Program, synthesis and assessment products by the U.S. Climate Change Science Program, assessment reports by the intergovernmental Panel on Climate Change, and
EPA's Climate Change Indicators in the United States. Mention of a particular season, location, species, or any other aspect of an impact does not imply anything about
the likelihood or importance of aspects that are not mentioned. For more information about climate change science, impacts, responses, and what you can do, visit EPA's
Climate Change website atwww.epa.gov/climatechanae.