United States	August 2016
Environmental Protection
Ugency	EPA 430-F-16-010
What Climate Change
Delaware's climate is changing. The state has warmed two
degrees (F) in the last century, heavy rainstorms are more
frequent, and the sea is rising about one inch every seven
years. Higher water levels are eroding beaches, submerging
low lands, exacerbating coastal flooding, and increasing the
salinity of estuaries and aquifers. In the coming decades,
changing the climate is likely to increase coastal flooding;
harm marine, wetland, and inland ecosystems; disrupt
farming; and increase some risks to human health.
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 warmed about one degree
during the last 80 years. Warming is causing snow to melt
earlier in spring, and mountain glaciers are retreating.
Even the great ice sheets on Greenland and Antarctica are
shrinking. Thus the sea is rising at an increasing rate.
Temperature change (°F):
-1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5
Rising temperatures in the iast century. Deiaware has warmed more
than most of the nation. Source: EPA, Climate Change Indicators in
the United States.
Increasing Temperature and Changing Precipitation
Rising temperatures and shifting rainfall patterns are likely to
increase the intensity of both floods and droughts. Average
annual precipitation in Delaware has increased a few percent in
the last century, and precipitation from extremely heavy storms
has increased in the eastern United States by more than
25 percent since 1958. During the next century, annual pre-
cipitation and the frequency of heavy downpours are likely to
keep rising. Precipitation is likely to increase during winter and
spring, but not change significantly during summer and fall.
Rising temperatures will melt snow earlier in spring and increase
evaporation, and thereby dry the soil during summer and fall. As
a result, climate change is likely to intensify flooding during
winter and spring, and drought during summer and fall.
Rising Seas and Retreating Shores
Sea level is rising more rapidly along the Delaware coast than in
most coastal areas because Delaware is sinking. If the oceans
and atmosphere continue to warm, sea level is likely to rise
between sixteen inches and four feet along the Delaware coast
in the next century.
As sea level rises, the lowest dry lands are submerged and
become either tidal wetland or open water. Wetlands can create
their own land and keep pace with a slowly rising sea. But if sea
level rises three feet or more in the next century, most existing
tidal wetlands in Delaware are unlikely to keep pace but will
instead become tidal mud flats or shallow open water. Exist-
ing tidal flats will generally convert to open water as they are
Beaches also erode as sea level rises. A higher ocean level makes
it more likely that storm waters will wash over a barrier island or
open new inlets. The United States Geological Survey estimates
that Fenwick Island could be broken up by new inlets or lost
to erosion if sea level rises three feet by the year 2100, unless
people take measures to reduce erosion. Estuarine beaches may
also be eliminated in some areas. Many of Delaware Bay's beach-
es are narrow, with wetlands immediately inland. Along parts of
Delaware Bay and the Delaware River, people have built walls or
other shore protection structures that eliminate the beach once
the shore erodes up to them.

Houses along Broadkill Beach
are vulnerable to severe storms,
flooding, and coastal erosion.
Credit: U.S. Army Corps of
Homes and Infrastructure
Towns along the Delaware shore
shore will be increasingly vulner-
able to storms and erosion as
sea level rises. While hurricanes
are rare, their wind speeds and
rainfall intensities are likely to
increase as the climate warms.
Rising sea level is likely to
increase flood insurance rates,
while more frequent storms
could increase deductibles for
wind damage in homeowner
insurance policies. Storms can destroy coastal homes, wash out
highways and rail lines, and damage essential communication,
energy, and wastewater management infrastructure.
The loss of tidal marshes could harm fish, reptiles, and birds
that depend on a marsh for food or shelter. Blue crab, perch,
weakfish, flounder, and rockfish rely on the tidal marshes in
Delaware Bay to hide from predators and to feed on mussels,
fiddler crabs, and other species. Sea turtles and shorebirds
feed on some of the species that inhabit these marshes. Great
blue herons, black ducks, ospreys, red-winged blackbirds, and
several other bird species also use the salt marshes in
Delaware Bay. As marshes erode, fish may benefit initially as
more tidal channels form, which would make more marsh
accessible. But after a point, erosion would make less marsh
available, and populations of fish and birds would decline.
The loss of bay beaches and tidal flats would also threaten some
species. Delaware Bay is a major stopover area for six species
of migratory shorebirds that feed on its beaches and tidal flats,
including most of the Western Hemisphere's red knot population.
Nearly a million birds feed on the horseshoe crab eggs on the
bay's sandy beaches. Diamondback terrapin nest on estuarine
beaches along Delaware's inland bays.
Changing temperatures could also disrupt ecosystems. If water
temperatures exceed 86°F during summer, eelgrass could be
lost, which would remove a key source of food for many fish.
Wildflowers and woody perennials are blooming—and migratory
birds are arriving—sooner in spring. Not all species adjust in the
same way, however, so the food that one species needs may no
longer be available when that species arrives on its migration.
Saltwater Intrusion
As sea level rises, salt water can mix farther inland or upstream
in bays, rivers, and wetlands. Because water on the surface
is connected to ground water, sait water can also intrude into
aquifers near the coast. Soils may become too salty for the crops
and trees that currently grow in low-lying areas.
Changing the climate will have both harmful and beneficial
effects on farming. Hotter summers are likely to reduce yields
of corn. But higher concentrations of atmospheric carbon
dioxide increase crop yields, and that fertilizing effect is likely
to offset the harmful effects of heat on soybeans, assuming
that adequate water is available. Although most chickens are
raised indoors, warmer temperatures could reduce the
productivity of livestock raised outside.
Human Health
Hot days can be unhealthy—even dangerous. Certain people
are especially vulnerable, including children, the elderly, the sick,
and the poor. High air temperatures can cause heat stroke and
dehydration, and affect people's cardiovascular and nervous
systems. Warmer temperatures can also increase the forma-
tion of ground-level ozone, a key component of smog that can
contribute to respiratory problems. Rising temperatures may also
increase the length and severity of the pollen season for plants
such as ragweed, which has already been observed in other
The risk of some diseases carried by insects may also increase.
The ticks that transmit Lyme disease are active when tempera-
tures are above 45°F, so warmer winters could lengthen the
season during which ticks can become infected or people can be
exposed to the ticks. The number of cases may or may not
increase, depending on what people do to control insect popula-
tions and avoid insect bites.
/Is sea level rises, the water table rises as well, which can prevent ordinary
septic systems from working properly. The owner of this house in Pickering
Beach responded by shifting to a mounds-based system, which provides
the required separation between the drain field and the water table.
© James G. Titus; used by permission.
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, ana 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.