Climate Change Indicators in the United States: Sea Surface Temperature
www.epa.gov/climatechange/indicators - Updated May 2014
Sea Surface Temperature
This indicator describes global trends in sea surface temperature.
Background
Sea surface temperature—the temperature of the water at the ocean surface—is an important physical
attribute of the world's oceans. The surface temperature of the world's oceans varies mainly with
latitude, with the warmest waters generally near the equator and the coldest waters in the Arctic and
Antarctic regions. As the oceans absorb more heat, sea surface temperatures will increase and the
ocean circulation patterns that transport warm and cold water around the globe will change.
Changes in sea surface temperature can alter marine ecosystems in several ways. For example,
variations in ocean temperature can affect what species of plants, animals, and microbes are present in
a location, alter migration and breeding patterns, threaten sensitive ocean life such as corals, and
change the frequency and intensity of harmful algal blooms such as "red tide."1 Over the long term,
increases in sea surface temperature could also reduce the circulation patterns that bring nutrients from
the deep sea to surface waters. Changes in reef habitat and nutrient supply could dramatically alter
ocean ecosystems and lead to declines in fish populations, which in turn could affect people who
depend on fishing for food or jobs.2
Because the oceans continuously interact with the atmosphere, sea surface temperature can also have
profound effects on global climate. Increases in sea surface temperature have led to an increase in the
amount of atmospheric water vapor over the oceans.3 This water vapor feeds weather systems that
produce precipitation, increasing the risk of heavy rain and snow (see the Heavy Precipitation and
Tropical Cyclone Activity indicators. Changes in sea surface temperature can also shift storm tracks,
potentially contributing to droughts in some areas.4
About the Indicator
This indicator tracks average global sea surface temperature from 1880 through 2013. It also includes a
map to show how change in sea surface temperature has varied across the world's oceans since 1901.
Techniques for measuring sea surface temperature have evolved since the 1800s. For instance, the
earliest data were collected by inserting a thermometer into a water sample collected by lowering a
bucket from a ship. Today, temperature measurements are collected more systematically from ships, as
well as at stationary and drifting buoys.
The National Oceanic and Atmospheric Administration has carefully reconstructed and filtered the data
in Figure 1 to correct for biases in the different collection techniques and to minimize the effects of
sampling changes over various locations and times. The data are shown as anomalies, or differences,
compared with the average sea surface temperature from 1971 to 2000. The map in Figure 2 was
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Climate Change Indicators in the United States: Sea Surface Temperature
www.epa.gov/climatechange/indicators - Updated May 2014
developed by the Intergovernmental Panel on Climate Change, which calculated long-term trends based
on a collection of published studies.
• Sea surface temperature increased over the 20th century and continues to rise. From 1901
through 2013, temperatures rose at an average rate of 0.13°F per decade (see Figure 1).
• Sea surface temperatures have been higher during the past three decades than at any other
time since reliable observations began in 1880 (see Figure 1).
• Increases in sea surface temperature have largely occurred over two key periods: between 1910
and 1940, and from about 1970 to the present. Sea surface temperatures appear to have cooled
between 1880 and 1910 (see Figure 1).
• Changes in sea surface temperature vary regionally. While most parts of the world's oceans
have seen temperatures rise, a few areas have actually experienced cooling—for example, parts
of the North Atlantic (see Figure 2).
Key Points
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Climate Change Indicators in the United States: Sea Surface Temperature
www.epa.gov/climatechange/indicators - Updated May 2014
Figure 1. Average Global Sea Surface Temperature, 1880-2013
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Climate Change Indicators in the United States: Sea Surface Temperature
www.epa.gov/climatechange/indicators - Updated May 2014
Figure 2. Change in Sea Surface Temperature, 1901-2012
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Change In sea surface temperature (°F):
-r
-1 -0.5 0
0.5 1 1.5 2 2.5 3 3,5 4
+ = statistically significant trend
Insufficient
data
This map shows how average sea surface temperatures around the world changed between 1901 and
2012. It is based on a combination of direct measurements and satellite measurements. A black "+"
symbol in the middle of a square on the map means the trend shown is statistically significant. White
areas did not have enough data to calculate reliable long-term trends.
Data source: IPCC, 2013°
Indicator Notes
Both components of this indicator are based on instrumental measurements of surface water
temperature. Due to denser sampling and improvements in sampling design and measurement
techniques, newer data are more precise than older data. The earlier trends shown by this indicator
have less certainty because of lower sampling frequency and less precise sampling methods, as shown
by the width of the blue shaded band in Figure 1.
Data Sources
Data for Figure 1 were provided by the National Oceanic and Atmospheric Administration's National
Climatic Data Center and are available online at: www.ncdc.noaa.gov/ersst. These data were
reconstructed from measurements of water temperature, which are available from the National Oceanic
and Atmospheric Administration at: http://icoads.noaa.gov/products.html. Figure 2 comes from the
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Climate Change Indicators in the United States: Sea Surface Temperature
www.epa.gov/climatechange/indicators - Updated May 2014
Intergovernmental Panel on Climate Change's Fifth Assessment Report (www.ipcc.ch/report/ar5/wgl),
which gathers data from a variety of studies that provide the best available information about climate
change.
1 For example, see: Ostrander, G.K., K.M. Armstrong, E.T. Knobbe, D. Gerace, and E.P. Scully. 2000. Rapid
transition in the structure of a coral reef community: The effects of coral bleaching and physical disturbance. P.
Natl. Acad. Sci. USA. 97(10):5297-5302.
2 Pratchett, M.S., S.K. Wilson, M.L. Berumen, and M.I. McCormick. 2004. Sublethal effects of coral bleaching on an
obligate coral feeding butterflyfish. Coral Reefs 23(3):352-356.
3 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis.
Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge
University Press, www.ipcc.ch/report/ar5/wgl.
4 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis.
Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge
University Press, www.ipcc.ch/report/ar5/wgl.
5 NOAA (National Oceanic and Atmospheric Administration). 2014. Extended reconstructed sea surface
temperature (ERSST.v3b). National Climatic Data Center. Accessed March 2014. www.ncdc.noaa.gov/ersst.
6 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis.
Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge
University Press, www.ipcc.ch/report/ar5/wgl.
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