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| U.S. and Global Temperature |
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 Climate Change Indicators: U.S. and
Global Temperature
This indicator describes trends in average surface
temperature for the United States and the world.
Key Points
Since 1901, the average surface temperature across the
contiguous 48 states has risen at an average rate of 0.14°F
per decade (see Figure 1). Average temperatures have risen
more quickly since the late 1970s (0.29 to 0.46°F per decade
since 1979). Eight of the top 10 warmest years on record for
the contiguous 48 states have occurred since 1998, and 2012
and 2015 were the two warmest years on record.
Worldwide, 2015 was the warmest year on record and 2006–2015
was the warmest decade on record since thermometer-based
observations began. Global average surface temperature has
risen at an average rate of 0.15°F per decade since 1901
(see Figure 2), similar to the rate of warming within the
contiguous 48 states. Since the late 1970s, however, the
United States has warmed faster than the global rate.
Some parts of the United States have experienced more
warming than others (see Figure 3). The North, the West, and
Alaska have seen temperatures increase the most, while some
parts of the Southeast have experienced little change. Not
all of these regional trends are statistically significant,
however. |
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Background
Temperature is a fundamental measurement for describing the
climate, and the temperature in particular places can have
wide-ranging effects on human life and ecosystems. For
example, increases in air temperature can lead to more
intense heat waves, which can cause illness and death,
especially in vulnerable populations. Annual and seasonal
temperature patterns also determine the types of animals and
plants that can survive in particular locations. Changes in
temperature can disrupt a wide range of natural processes,
particularly if these changes occur more quickly than plant
and animal species can adapt.
Concentrations of heat-trapping greenhouse gases are
increasing in the Earth’s atmosphere (see the Atmospheric
Concentrations of Greenhouse Gases indicator). In response,
average temperatures at the Earth’s surface are increasing
and are expected to continue rising. Because climate change
can shift the wind patterns and ocean currents that drive
the world’s climate system, some areas are warming more than
others, and some have experienced cooling. |
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About the Indicator
This indicator examines U.S. and global surface temperature
patterns over time. U.S. surface measurements come from
weather stations on land, while global surface measurements
also incorporate observations from buoys and ships on the
ocean, thereby providing data from sites spanning much of
the surface of the Earth. This indicator starts at 1901
except for the detailed map of Alaska, where reliable
statewide records are available back to 1925. For
comparison, this indicator also displays satellite
measurements that can be used to estimate the temperature of
the Earth’s lower atmosphere since 1979.
This indicator shows annual anomalies, or differences,
compared with the average temperature from 1901 to 2000. For
example, an anomaly of +2.0 degrees means the average
temperature was 2 degrees higher than the long-term average.
Anomalies have been calculated for each weather station.
Daily temperature measurements at each site were used to
calculate monthly anomalies, which were then averaged to
find an annual temperature anomaly for each year. Anomalies
for the contiguous 48 states and Alaska have been determined
by calculating average anomalies for areas within each state
based on station density, interpolation, and topography.
These regional anomalies are then averaged together in
proportion to their area to develop national results.
Similarly, global anomalies have been determined by dividing
the world into a grid, averaging the data for each cell of
the grid, and then averaging the grid cells together.
Indicator Notes
Data from the early 20th century are somewhat less precise
than more recent data because there were fewer stations
collecting measurements at the time, especially in the
Southern Hemisphere. The overall trends are still reliable,
however. Where possible, the data have been adjusted to
account for any biases that might be introduced by factors
such as station moves, urbanization near the station,
changes in measuring instruments, and changes in the exact
times at which measurements are taken.
Hawaii and U.S. territories are not included, due to
limitations in available data.
Data Sources
The data for this indicator were provided by the National
Oceanic and Atmospheric Administration’s National Centers
for Environmental Information, which maintains a large
collection of climate data online at:
www.ncei.noaa.gov. The
surface temperature anomalies shown here were calculated
based on monthly values from a network of long-term
monitoring stations. Satellite data were analyzed by two
independent groups—the Global Hydrology and Climate Center
at the University of Alabama in Huntsville (UAH) and Remote
Sensing Systems (RSS)—resulting in slightly different trend
lines.
Technical Documentation
Download related technical information PDF |
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 Figure
1. Temperatures in the Contiguous 48 States, 1901–2015
This figure shows how annual average temperatures in the
contiguous 48 states have changed since 1901. Surface data
come from land-based weather stations. Satellite
measurements cover the lower troposphere, which is the
lowest level of the Earth’s atmosphere. “UAH” and “RSS”
represent two different methods of analyzing the original
satellite measurements. This graph uses the 1901–2000
average as a baseline for depicting change. Choosing a
different baseline period would not change the shape of the
data over time.
Data source: NOAA, 20161 |
 Figure
2. Temperatures Worldwide, 1901–2015
This figure shows how annual average temperatures worldwide
have changed since 1901. Surface data come from a combined
set of land-based weather stations and sea surface
temperature measurements. Satellite measurements cover the
lower troposphere, which is the lowest level of the Earth’s
atmosphere. “UAH” and “RSS” represent two different methods
of analyzing the original satellite measurements. This graph
uses the 1901–2000 average as a baseline for depicting
change. Choosing a different baseline period would not
change the shape of the data over time.
Data source: NOAA, 20162 |
 Figure
3. Rate of Temperature Change in the United States,
1901–2015
This figure shows how annual average air temperatures have
changed in different parts of the United States since the
early 20th century (since 1901 for the contiguous 48 states
and 1925 for Alaska). The data are shown for climate
divisions, as defined by the National Oceanic and
Atmospheric Administration.
Data source: NOAA, 20163 |
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EPA Page |
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This is the
EPA page for this topic. To see if the Trump
administration has changed the EPA page, simply click the
link and compare the information with this page. If you
notice changes were made to the EPA page, please post a
comment. Thanks. |
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Additional Climate Change Information |
Climate Change and Carbon Dioxide
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change
and carbon dioxide.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice. |
Carbon Dioxide and Climate Change
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of carbon dioxide
and climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice. |
Environmental Group Warns Earth's Health at Risk
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
A report by the World Wildlife Fund looked at thousands of animal populations
and found they have dropped significantly in 40 years. |
Sea Levels Rising at Fastest Rate in 3,000 years
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
A group of scientists say sea levels are rising at record rates. Another group
found that January temperatures in the Arctic reached a record high. |
Capturing CO2 Gas Is Not Easy
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
Most scientists agree that carbon-dioxide gas is partly to blame for climate
change: rising global temperatures. But capturing the CO2 gas released by power
stations is costly and difficult. |
Growth, Climate Change Threaten African Plants and
Animals
(Beginner - Listening,
reading)
A video lesson to
help with your understanding of climate change.
The English is
spoken at 75% of normal speed.
Great English listening and reading practice.
Researchers believe Africa may lose as much as 30 percent of its animal and
plant species by the end of this century. |
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