ifik |-r%J% United States
1 Environmental Protection
%.»r it—i w mAgency
August 2016 ^
EPA 430-F-16-016
What Climate Change


Indiana's climate is changing. Most of the state has
warmed 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
temperatures 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 3.5
Rising temperatures in the last century. Northern Indiana has
warmed more than southern Indiana. Source: EPA, Climate
Change Indicators in the United States.
Heavy Precipitation and Flooding
Changing the climate is likely to increase the frequency of
floods in Indiana, 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.
Ohio River
Flooding occasionally
threatens both navigation
and riverfront communities,
and greater river flows
could increase these
One advantage of climate change is that warmer winters
reduce the number of days that ice prevents navigation.
threats. In 2011, a com-
bination of heavy rainfall
and melting snow caused
flooding along the Ohio	Heavy rain flooded the Wabash
and Wabash rivers in Southern River in March 2009, including
Indiana and closed the lower this section north of Lafayette.
Ohio River to navigation. Credit; Ashley Brooks, National
Weather Seivice.
Although springtime in Indiana
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 2005 caused portions of
the lower Ohio River to be closed to commercial navigation,
which delayed shipments of crops and other products to and
from upstream states like Indiana. In 2012, a drought caused
navigation restrictions on the lower Mississippi River, which
cost the region more than $275 million.

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, the 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 the 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, much of
Indiana is likely to have 5 to 15 more days per year with
temperatures above 95°F than it has today. More severe
droughts or floods would also hurt crop yields.
Increasingly hot summers and droughts could reduce yields of corn.
Credit; USD A Natural Resources Conservation Service.
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 Indiana,
ozone levels are high enough to significantly reduce yields of
soybeans and winter wheat. EPA and the Indiana Department
of Environmental Management have been working to reduce
ozone concentrations. As the climate changes, continued
progress toward clean air will become more difficult.
Hot days can be unhealthy—even dangerous. High air tem-
peratures can cause heat stroke and dehydration, and affect
people's cardiovascular and nervous systems. Midwestern
cities like Indianapolis are vulnerable to heat waves, because
many houses and apartments lack air conditioning, and urban
areas are typically warmer than their rural surroundings. In
recent decades, severe heat waves have killed hundreds of
people across the Midwest. Heat stress is expected to increase
as climate change brings hotter summer temperatures and
more humidity. 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.