United States
Environmental Protection
Agency
Climate Change
Indicators in the
United States, 2012
EPA's Climate Change Indicators in the United States, 2012,
presents compelling evidence that many fundamental
measures of climate in the United States are changing.
Temperatures are rising, snow and rainfall patterns are shifting,
and more extreme climate events—like heavy rainstorms and
record-high temperatures—are already affecting society and
ecosystems. Similar changes are occurring around the world.
EPA's report presents 26 indicators, which are organized into the
five categories listed at right.
Observed Changes
A Greenhouse
, . Gases:
Greenhouse
gas emissions
are increasing
as a result
of people's
activities. Consequently, average
concentrations of these heat-
trapping gases in the atmosphere
are also increasing.
Weather
and Climate:
Average U.S.
ind global
emperatures
ire increasing.
:es of weather and
_ , as precipitation,
drought, and tropical cyclone
activity, are changing.
Oceans: The
oceans are
getting warmer.
Sea levels are
rising around the
world, and the
coming more acidic.
Snow and Ice:
The extent of
Arctic sea ice
is declining.
Glaciers in
the United
States and around the world are
Oenerally shrinking, while snowfall
and snow cover in the United
States have decreased overall.
Society and
systems:
;weed
pollen season
as is the
growing season for crops.
Winter habitats of bird species
have shifted northward as
temperatures have risen.
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Climate Change In
Atmospheric
Concentrations of
Greenhouse Gases
Before the industrial era began in
the late 1700s, global carbon dioxide
concentrations in the atmosphere
measured approximately 280 parts
per million (ppm). Concentrations
have risen steadily since then, reaching
391 ppm in 2011—a 40 percent
increase. Current global atmospheric
concentrations of carbon dioxide are
unprecedented compared with the
past 650,000 years.
Global Atmospheric Concentrations
of Carbon Dioxide Over lime
-650,000 years ago to present
400
.1 30°
~ 250
w
u
200
u
at
150
100
•S 50
CO
Sea Level
As temperatures rise,
seawater warms up and
expands, and ice melts.
This raises sea level
worldwide. Sea level
rose relative to the land
along much of the U.S.
coastline between I960
and 2011, particularly
along the Mid-Atlantic
and Gulf Coasts. Some
parts of the Gulf Coast
have registered a relative
sea level rise of more
than 8 inches since I960.
-700,000 -500,000 -300,000 -100,000 0
Year [negative values = BO
Data source: Compilation of 12 underlying datasets
Relative Sea Level Change
Along U.S. Coasts, 1960-2011
H I
Hawaii and
-, Pacific Islands
tit
f
~|
Relative sea level change [inches]:
„ -7.99 -5.99 -3.99 -1.99
s-8 to-6 to-4 to-2 toO
t t
1
0.01 2.01 4.01 6.01 >8
to2 to4 to6 to8
Data source: NOAA, 2012
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cheater Highlights
Snowfall
With warming temperatures
and changing weather patterns,
snowfall amounts have
decreased in many parts of
the country (as indicated by
the red circles on the map),
with 57 percent of weather
stations showing a decline. The
Pacific Northwest has seen
the largest consistent decline
in snowfall, but some regions
have experienced modest
increases, including areas near
the Great Lakes.
Change in Total Snowfall in the
Contiguous 48 States, 1930-2007
Rate of change (percent per year):
<-1.2 -0.9 -0.6 -0.3 -0.1 -0.1 0.1 0.3 0.6 0.9
to -1.2 to -0.9 to -0.6 to -0.3 to 0.1 to 0.3 to 0.6 to 0.9 to 1.2
Less snowfall
>1.2
->
More snowfall
Data source: Kunkel et al., 2009
High and Low Temperatures
Since the 1970s, record-setting daily high temperatures
have become more common than record lows across
the United States. The most recent decade had twice
as many record highs as record lows.
Record Daily High and Low Temperatures
in the Contiguous 48 States, 1950-2009
100
I Record hig hs • Record lows
Ragweed Pollen Season
The length of the ragweed pollen season is closely
related to the timing of the first fall frost, which is
occurring later than it used to in northern areas.
Since 1995, the ragweed pollen season has grown
longer at eight of the 10 locations studied. The
red circles represent a longer pollen season, with
larger circles indicating larger changes.
Change in Ragweed Pollen Season, 1995-2011
|+26 days
1950s 1960s 1970s 1980s 1990s 2000s
Decade
+18 days
.+24 days
—+21 days
-+14 days
>+13 days
• +12 days
i+12 days
Change in length
of pollen season:
• Decrease
• Increase
-Iday
-Iday
Data source: Ziska et al., 20
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imate
Indicators
Greenhouse Gases
U.S. Greenhouse Gas Emissions
Global Greenhouse Gas
Emissions
Atmospheric Concentrations
of Greenhouse Gases
Climate Forcing
Weather and Climate
U.S. and Global Temperature
High and Low Temperatures
U.S. and Global Precipitation
Heavy Precipitation
Drought
Tropical Cyclone Activity
Oceans
Ocean Heat
Sea Surface Temperature
Sea Level
Ocean Acidity
Snow and Ice
Arctic Sea Ice
Glaciers
Lake Ice
Snowfall
Snow Cover
Snowpack
Society and Ecosystems
Streamflow
Ragweed Pollen Season
Length of Growing Season
Leaf and Bloom Dates
Bird Wintering Ranges
Heat-Related Deaths
Access the 2012 Report Online
www.epa.gov/climatechange/indicators
For each of the 26
indicators, the report
presents graphics depicting
changes over time, key
points about what the
graphics show, background
on how the indicator relates
to climate change, and
information about how the
indicator was developed.
The website also features
technical documentation
that provides additional
details about each indicator. Visitors to the website can share report
content through social media outlets like Facebook and Twitter.
A print version of the report is available by request or for download
from the website.
«, U.S. and Global Precipitation
Indicator Notes
Background
Figure I. Pndpilitiin In the Contiguous « States. 19QM011 Figure 3. Rate of Precipitation Chtnge In the United Stales,
United States
Environmental Protection
i Agency
Order Print Copies
Print copies of Climate Change
Indicators in the United States,
20/2, are available upon request.
To order a copy, please submit a
written request to:
climateindicators@epa.gov
Connect with EPA!
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§? youtube.com/user/USEPAgov
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December 2012
EPA430-F-I2-032
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