United States	AliOUSt 2016
Environmental Protection	y
Aflency	EPA 430-F-16-030
3-EPA
What Climate Change
/wea/7S for Nevada

Nevada's climate is changing. The state has warmed
about two degrees (F) in the last century. Throughout
the southwestern United States, heatwaves are
becoming more common, and snow is melting earlier in
spring. In the coming decades, the changing climate is
likely to decrease the flow of water in the Colorado and
other rivers in Nevada, increase the frequency and
intensity of wildfires, and decrease the productivity of
ranches and farms.
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 one degree during
the last 80 years. Warming is causing snow to melt
earlier in spring.
Snowpack
As the climate warms, less precipitation falls as snow, and more snow
melts during the winter. That decreases snowpack—the amount of snow
that accumulates over the winter. Since the 1950s, snowpack has declined
in Nevada, as well as in the other states in the Colorado River Basin.
Diminishing snowpack can shorten the season for skiing and other forms of
winter tourism and recreation. The tree line may shift, as subalpine fir and
other high-altitude trees become able to grow at higher elevations. A higher
tree iine would decrease the extent of alpine tundra ecosystems, which
could threaten some species.
Water Availability
The changing climate is likely to increase the need for water but reduce the
supply. Higher temperatures increase the rate at which water evaporates
(or transpires) into the air from soils, plants, and surface waters. Irrigated
farmland would thus need more water. But less water is likely to be
available, because precipitation is unlikely to increase enough to make up
for the additional water lost to evaporation. Annual rainfall is more likely to
decrease than increase. So soils are likely to be drier, and periods without
rain are likely to become longer, making droughts more severe.
Temperature change (°F):
-t -0.5 0 0.5 1 1.5 2 2.5 3 3.5
Rising temperatures in the last century. The last decade
was the warmest on record in the Southwest. Source: EPA,
Climate Change Indicators in the United States.
Lake Mead viewed from Hoover Dam in 2009. Decreased flows in the Colorado
River have lowered the water level, which prompted the Southern Nevada Water
Authority to build a new drinking water intake that could supply Las Vegas even
if the lake falls below Hoover Dam's lowest outlet. © Chris Lamie; used by
peimission.

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The decline in snowpack could further limit the supply of water for
some purposes. Mountain snowpacks are natural reservoirs. They
collect the snow that falls during winter and release water when the
snow melts during spring and summer. Over the past 50 years,
snowpack has been melting earlier in the year. Dams capture most
meltwater and retain it for use later in the year. But upstream of
these reservoirs, less water is available during droughts for ecosys-
tems, fish, water-based recreation, and landowners who draw
water directly from a flowing river.
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Sources: Esri, DeLorme, USGS, NPS, Sources:
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Snowpack, 1955-2015 Percent Change
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Colorado River Basin


Trends in April snowpack in Nevada and the Colorado River Basin, 1955-
2013. Snowpack has decreased at most monitoring sites. Source: EPA,
Agriculture
Increasing droughts and higher temperatures are likely to interfere
with Nevada's farms and cattle ranches. Less water is likely to be
available for ranches or farmers who irrigate crops. Hot weather
can threaten cows' health and cause them to eat less, grow more
slowly, and produce iess milk. Livestock operations could be
further impaired by fire and changes in the landscape from
grassland to woody shrubs more typical of a desert.
Wildfires and Changing Landscapes
Higher temperatures and drought are likely to increase the severity,
frequency, and extent of wildfires in Nevada, which could harm
property, livelihoods, and human health. On average, about
5 percent of the land in Nevada has burned per decade since 1984,
Wildfire smoke can reduce air quality and increase medical visits for
chest pains, respiratory problems, and heart problems.
In 2005, the Southern Nevada Complex Fire burned more than half a
million acres, making it the largest wildfire in the state's recorded history.
Credit: Bureau of Land Management, Ely Field Office files.
The combination of more fires and drier conditions may change
parts of Nevada's landscape. Many plants and animals living in arid
lands are already near the limits of what they can tolerate, in some
cases, native vegetation may persist as the climate changes. But
when drought, grazing, or fire destroy the natural cover, native
plants may be replaced by non-native grasses. Because non-native
grasses are generally more prone to intense fires, native plants
may be unable to re-establish themselves.
Pests
Warmer and drier conditions also make forests more susceptible
to pests. Droughts reduce the ability of trees to mount a defense
against attacks from pests such as bark beetles, which infested
28,000 acres of Nevada's forests in 2014. Temperature controls
the life cycle and winter mortality rates of many pests. With higher
winter temperatures, some pests can persist year-round, and new
pests and diseases may become established.
Human Health
Hot days can be unhealthy—even dangerous. Certain people are
especially vulnerable, including children, the elderly, the sick, and
the poor. High temperatures can cause dehydration and heat
stroke, and affect people's cardiovascular, respiratory, and
nervous systems. Higher temperatures are amplified in urban
settings where paved and other surfaces tend to store heat.
Construction crews may have to increasingly operate on altered
time schedules to avoid the heat of the day.
Rising temperatures can also increase the formation of ground-
level ozone, a key component of smog. Ozone has a variety of
health effects, aggravates lung diseases such as asthma, and
increases the risk of premature death from heart or lung disease.
EPA and the Nevada Division of Environmental Protection have been
working to reduce ozone concentrations. As the climate changes,
continued progress toward clean air will become more difficult.
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
at www.epa.aov/climatechanae.

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