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Climate Change Indicators

Climate Change Indicators: Greenhouse Gases

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Greenhouse gases from human activities are the most significant driver of observed climate change since the mid-20th century.1Â The indicators in this chapter characterize emissions of the major greenhouse gases resulting from human activities, the concentrations of these gases in the atmosphere, and how emissions and concentrations have changed over time. When comparing emissions of different gases, these indicators use a concept called â€œglobal warming potentialâ€? to convert amounts of other gases into carbon dioxide equivalents.

Why does it matter?

As greenhouse gas emissions from human activities increase, they build up in the atmosphere and warm the climate, leading to many other changes around the worldâ€”in the atmosphere, on land, and in the oceans. The indicators in other chapters of this report illustrate many of these changes. These changes have both positive and negative effects on people, society, and the environmentâ€”including plants and animals. Because many of the major greenhouse gases stay in the atmosphere for tens to hundreds of years after being released, their warming effects on the climate persist over a long time and can therefore affect both present and future generations.

Summary of Key Points

U.S. Greenhouse Gas Emissions. In the United States, greenhouse gas emissions caused by human activities increased by 7 percent from 1990 to 2014. Since 2005, however, total U.S. greenhouse gas emissions have decreased by 7 percent. Carbon dioxide accounts for most of the nationâ€™s emissions and most of the increase since 1990. Electricity generation is the largest source of greenhouse gas emissions in the United States, followed by transportation. Emissions per person have decreased slightly in the last few years.

Sources of Data on U.S. Greenhouse Gas Emissions. EPA has two key programs that provide data on greenhouse gas emissions in the United States: the Inventory of U.S. Greenhouse Gas Emissions and Sinks and the Greenhouse Gas Reporting Program. The programs are complementary, providing both a higher-level perspective on the nationâ€™s total emissions and detailed information about the sources and types of emissions from individual facilities.

Global Greenhouse Gas Emissions. Worldwide, net emissions of greenhouse gases from human activities increased by 35 percent from 1990 to 2010. Emissions of carbon dioxide, which account for about three-fourths of total emissions, increased by 42 percent over this period. As with the United States, the majority of the worldâ€™s emissions result from electricity generation, transportation, and other forms of energy production and use.

Atmospheric Concentrations of Greenhouse Gases. Concentrations of carbon dioxide and other greenhouse gases in the atmosphere have increased since the beginning of the industrial era. Almost all of this increase is attributable to human activities.2 Historical measurements show that the current global atmospheric concentrations of carbon dioxide are unprecedented compared with the past 800,000 years, even after accounting for natural fluctuations.

Climate Forcing. Climate forcing refers to a change in the Earthâ€™s energy balance, leading to either a warming or cooling effect over time. An increase in the atmospheric concentrations of greenhouse gases produces a positive climate forcing, or warming effect. From 1990 to 2015, the total warming effect from greenhouse gases added by humans to the Earthâ€™s atmosphere increased by 37 percent. The warming effect associated with carbon dioxide alone increased by 30 percent.

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Major Long-Lived Greenhouse Gases and Their Characteristics

Greenhouse gas
			How it's produced
			Average lifetime in the atmosphere
			100-year global warming potential

Carbon dioxide
			Emitted primarily through the burning of fossil fuels (oil, natural gas, and coal), solid waste, and trees and wood products. Changes in land use also play a role. Deforestation and soil degradation add carbon dioxide to the atmosphere, while forest regrowth takes it out of the atmosphere.Â
			see below*
			1

Methane
			Emitted during the production and transport of oil and natural gas as well as coal. Methane emissions also result from livestock and agricultural practices and from the anaerobic decay of organic waste in municipal solid waste landfills.Â
			12.4 years
			28â€“36

Nitrous oxide
			Emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.Â
			121 years
			265â€“298

Fluorinated gases
			A group of gases that contain fluorine, including hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, among other chemicals. These gases are emitted from a variety of industrial processes and commercial and household uses and do not occur naturally. Sometimes used as substitutes for ozone-depleting substances such as chlorofluorocarbons (CFCs).Â
			A few weeks to thousands of years
			Varies (the highest is sulfur hexfluoride at 23,500

This table shows 100-year global warming potentials, which describe the effects that occurÂ over a period ofÂ 100 years after aÂ particular mass of aÂ gas is emitted.Â Global warming potentialsÂ and lifetimes come from theÂ Intergovernmental Panel on Climate Changeâ€™s Fifth Assessment Report.3

* Carbon dioxideâ€™s lifetimeÂ cannot be represented with a single valueÂ because the gas is not destroyed over time, but instead movesÂ amongÂ different parts of the oceanâ€“atmosphereâ€“land system. Some of the excess carbon dioxideÂ isÂ absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years, due in part to the very slow process by which carbon is transferred to ocean sediments.

Sources of Data on U.S. Greenhouse Gas Emissions

EPA has two key programs that provide data on greenhouse gas emissions in the United States: the Inventory of U.S. Greenhouse Gas Emissions and Sinks and the Greenhouse Gas Reporting Program. The programs are complementary, providing both a higher-level perspective on the nationâ€™s total emissions and detailed information about the sources and types of emissions from individual facilities. The data in EPAâ€™s U.S. Greenhouse Gas Emissions indicator come from the national inventory.

EPA's Inventory of Greenhouse Gas Emissions and Sinks

EPA develops an annual report called theÂ Inventory of U.S. Greenhouse Gas Emissions and SinksÂ (or the GHG Inventory). This report tracks trends in total annual U.S. emissions by source (or sink), economic sector, and greenhouse gas going back to 1990. EPA uses national energy data, data on national agricultural activities, and other national statistics to provide a comprehensive accounting of total greenhouse gas emissions for all man-made sources in the United States. This inventory fulfills the nationâ€™s obligation to provide an annual emissions report under the United Nations Framework Convention on Climate Change.

Learn more about the inventory and explore the dataÂ using interactive tools.

EPA's Greenhouse Gas Reporting Program

EPAâ€™s Greenhouse Gas Reporting Program collects annual emissions data from industrial sources that directly emit large amounts of greenhouse gases. Generally, facilities that emit more than 25,000 metric tons of carbon dioxide equivalents per year are required to report. The program also collects data from entities known as "suppliers" that supply certain fossil fuels and industrial gases that will emit greenhouse gases into the atmosphere if burned or releasedâ€”for example, refineries that supply petroleum products such as gasoline. The Greenhouse Gas Reporting Program only requires reporting; it is not an emissions control program. This program helps EPA and the public understand where greenhouse gas emissions are coming from, and will improve our ability to make informed policy, business, and regulatory decisions.

EPAâ€™s Greenhouse Gas Reporting Program provides facility-level information and allows people to track changes in greenhouse gas emissions in various industries, geographic areas, and industrial facilities. EPA has now verified three years of data and made them publicly available.

Learn more about the Greenhouse Gas Reporting Program and explore dataÂ by facility, industry, location, or gas using a data visualization and mapping tool called FLIGHT.

References

1 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/wg1.

2 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/wg1.

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/wg1.

Climate Indicators

Climate Change Indicators

Greenhouse Gases

U.S. Greenhouse Gas Emissions

Global Greenhouse Gas Emissions

Atmospheric Concentrations of Greenhouse Gases

Climate Forcing

Weather and Climate

Oceans

Snow and Ice

Health and Society

Ecosystems

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Community Connection: Cherry Blossom Bloom Dates in Washington, D.C.

This feature tracks the annual peak bloom date of Washington, D.C.’s famous cherry trees.

Figure 1. Peak Bloom Date for Cherry Trees Around Washington, D.C.’s Tidal Basin, 1921–2016

This figure shows the peak bloom date each year for the main type of cherry tree around the Tidal Basin in Washington, D.C. The peak bloom date occurs when 70 percent of the blossoms are in full bloom. The shaded band shows the timing of the annual National Cherry Blossom Festival. The festival began in 1934 but was not held during World War II.

Data sources: National Cherry Blossom Festival, 2016;2 National Park Service, 20153
Web update: April 2016

Figure 1. Peak Bloom Date for Cherry Trees Around Washington, D.C.’s Tidal Basin, 1921–2016

Key Points

Background

Notes

Data Sources

Technical Documentation

Key Points

Based on the entire 96 years of data in Figure 1, Washington’s cherry blossoms reach their peak on April 4 in an average year. By comparison, the peak bloom date in 2016 was March 25.

Peak bloom date for the cherry trees is occurring earlier than it did in the past. Since 1921, peak bloom dates have shifted earlier by approximately five days.

While the length of the National Cherry Blossom Festival has continued to expand, the Yoshino cherry trees have bloomed near the beginning of the festival in recent years. During some years, the festival missed the peak bloom date entirely.

Background

In Washington, D.C., the arrival of spring brings a splash of color as the city’s iconic cherry trees burst into bloom. The city has enjoyed cherry blossoms each year dating back to 1912, when Japan gave about 3,000 cherry trees to the United States as a gift of friendship. These trees surround Washington’s Tidal Basin, and the beautiful blooms set against the backdrop of the national monuments bring more than 1.5 million visitors to the area every year during the National Cherry Blossom Festival. Not surprisingly, the festival is planned to coincide with the peak bloom of the cherry trees.

The exact timing of peak bloom varies from year to year, and it is largely driven by local temperatures during the winter and early spring. As the Leaf and Bloom Dates indicator explains, scientists have very high confidence that recent warming trends in global climate are causing spring events such as leaf growth and flower blooms to happen earlier.1 In the case of Washington’s cherry blossoms, earlier bloom dates could affect tourism and the local economy.

The peak bloom date for the most common type of cherry tree around Washington’s Tidal Basin—the Yoshino variety—has been carefully estimated and recorded since 1921 by the National Park Service. The peak bloom date is defined as the day when 70 percent of the blossoms are in full bloom.

Figure 1 shows how the peak bloom date of the Yoshino cherry trees has changed since 1921. It also shows the dates of the National Cherry Blossom Festival, which has grown to several weeks as its popularity has expanded. There is considerable variability in the peak bloom date, which makes predicting the exact timing difficult. Anticipation of the peak bloom captivates meteorologists, city planners, the National Park Service, residents, and tourists each year.

Notes

In addition to winter and early spring temperatures, the timing of the peak bloom for cherry trees can be affected by other weather, climate, and location factors. For example, extended growing periods and warmer autumns could affect bloom dates by altering other stages of cherry tree growth.4

Data Sources

Peak bloom dates and festival dates were provided by the National Park Service and organizers of the National Cherry Blossom Festival. Bloom dates and other information about Washington’s cherry trees can be found online at: www.nationalcherryblossomfestival.org and: www.nps.gov/subjects/cherryblossom/index.htm.

Technical Documentation

Download related technical information PDF

References

1 IPCC (Intergovernmental Panel on Climate Change). 2014. Climate change 2014: Impacts, adaptation, and vulnerability. Working Group II contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge University Press. www.ipcc.ch/report/ar5/wg2.

2 National Cherry Blossom Festival. 2016. Bloom watch. Accessed April 14, 2016. www.nationalcherryblossomfestival.org/about/bloom-watch.

3 National Park Service. 2015. Bloom schedule. Accessed April 24, 2015.

4 Chung, U., L. Mack, J.I. Yun, and S. Kim. 2011. Predicting the timing of cherry blossoms in Washington, D.C. and Mid-Atlantic states in response to climate change. PLoS ONE 6(11):e27439.

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Learn about other indicators in this section

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Wildfires

Streamflow

Stream Temperature

Tribal Connection: Trends in Stream Temperature in the Snake River

Great Lakes Water Levels and Temperatures

Bird Wintering Ranges

Marine Species Distribution

Leaf and Bloom Dates

Community Connection: Cherry Blossom Bloom Dates in Washington, D.C.

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EPA has published a new printed edition of Climate Change Indicators in the United States every two years, starting in 2010. This page provides access to previous editions, along with related fact sheets and brochures featuring content from the report. All of these publications are available below as downloadable PDF files.

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Climate Change Indicators: Sea Level

This indicator describes how sea level has changed over time. The indicator describes two types of sea level changes: absolute and relative.

Figure 1. Global Average Absolute Sea Level Change, 1880–2015

This graph shows cumulative changes in sea level for the world’s oceans since 1880, based on a combination of long-term tide gauge measurements and recent satellite measurements. This figure shows average absolute sea level change, which refers to the height of the ocean surface, regardless of whether nearby land is rising or falling. Satellite data are based solely on measured sea level, while the long-term tide gauge data include a small correction factor because the size and shape of the oceans are changing slowly over time. (On average, the ocean floor has been gradually sinking since the last Ice Age peak, 20,000 years ago.) The shaded band shows the likely range of values, based on the number of measurements collected and the precision of the methods used.

Data sources: CSIRO, 2015;3 NOAA, 20164
Web update: August 2016

Figure 2. Relative Sea Level Change Along U.S. Coasts, 1960–2015

This map shows cumulative changes in relative sea level from 1960 to 2015 at tide gauge stations along U.S. coasts. Relative sea level reflects changes in sea level as well as land elevation.

Data source: NOAA, 20165
Web update: August 2016

Figure 1. Global Average Absolute Sea Level Change, 1880–2015

Figure 2. Relative Sea Level Change Along U.S. Coasts, 1960–2015

			Key Points

			Background

About the

			Indicator

			Indicator Notes

			Data Sources

Technical

			Documentation

Key Points

After a period of approximately 2,000 years of little change (not shown here), global average sea level rose throughout the 20th century, and the rate of change has accelerated in recent years.1 When averaged over all of the world’s oceans, absolute sea level has risen at an average rate of 0.06 inches per year from 1880 to 2013 (see Figure 1). Since 1993, however, average sea level has risen at a rate of 0.11 to 0.14 inches per year—roughly twice as fast as the long-term trend.

Relative sea level rose along much of the U.S. coastline between 1960 and 2015, particularly the Mid-Atlantic coast and parts of the Gulf coast, where some stations registered increases of more than 8 inches (see Figure 2). Meanwhile, relative sea level fell at some locations in Alaska and the Pacific Northwest. At those sites, even though absolute sea level has risen, land elevation has risen more rapidly.

While absolute sea level has increased steadily overall, particularly in recent decades, regional trends vary, and absolute sea level has decreased in some places.2  Relative sea level also has not risen uniformly because of regional and local changes in land movement and long-term changes in coastal circulation patterns.

Background

As the temperature of the Earth changes, so does sea level. Temperature and sea level are linked for two main reasons:

Changes in the volume of water and ice on land (namely glaciers and ice sheets) can increase or decrease the volume of water in the ocean (see the Glaciers indicator).

As water warms, it expands slightly—an effect that is cumulative over the entire depth of the oceans (see the Ocean Heat indicator).

Changing sea levels can affect human activities in coastal areas. Rising sea level inundates low-lying wetlands and dry land, erodes shorelines, contributes to coastal flooding, and increases the flow of salt water into estuaries and nearby groundwater aquifers. Higher sea level also makes coastal infrastructure more vulnerable to damage from storms.

The sea level changes that affect coastal systems involve more than just expanding oceans, however, because the Earth’s continents can also rise and fall relative to the oceans. Land can rise through processes such as sediment accumulation (the process that built the Mississippi River delta) and geological uplift (for example, as glaciers melt and the land below is no longer weighed down by heavy ice). In other areas, land can sink because of erosion, sediment compaction, natural subsidence (sinking due to geologic changes), groundwater withdrawal, or engineering projects that prevent rivers from naturally depositing sediments along their banks. Changes in ocean currents such as the Gulf Stream can also affect sea levels by pushing more water against some coastlines and pulling it away from others, raising or lowering sea levels accordingly.

Scientists account for these types of changes by measuring sea level change in two different ways. Relative sea level change refers to how the height of the ocean rises or falls relative to the land at a particular location. In contrast, absolute sea level change refers to the height of the ocean surface above the center of the earth, without regard to whether nearby land is rising or falling.

About the Indicator

This indicator presents trends in sea level based on measurements from tide gauges and from satellites that orbit the Earth. Tide gauges measure relative sea level change at points along the coast, while satellite instruments measure absolute sea level change over nearly the entire ocean surface. Many tide gauges have collected data for more than 100 years, while satellites have collected data since the early 1990s.

Figure 1 shows annual absolute sea level change averaged over the entire Earth’s ocean surface. The long-term trend is based on tide gauge data that have been adjusted to show absolute global trends through calibration with recent satellite data. This long-term data set has been calculated through 2013, while satellite data are now available through the end of 2015. Figure 2 shows trends at a more local scale, highlighting the 1960 to 2015 change in relative sea level at 67 tide gauges along the Atlantic, Pacific, and Gulf coasts of the United States.

Indicator Notes

Relative sea level trends represent a combination of absolute sea level change and any local land movement. Tide gauge measurements such as those in Figure 2 generally cannot distinguish between these two different influences without an accurate measurement of vertical land motion nearby.

Some changes in relative and absolute sea level can be due to multi-year cycles such as El Niño and La Niña, which affect coastal ocean temperatures, salt content, wind patterns, atmospheric pressure (and thus storm tracks), and currents. Obtaining a reliable trend can require many years of data, which is why the satellite record in Figure 1 has been supplemented with a longer-term reconstruction based on tide gauge measurements.

Data Sources

Absolute sea level trends were provided by Australia’s Commonwealth Scientific and Industrial Research Organisation and the National Oceanic and Atmospheric Administration. These data are based on measurements collected by satellites and tide gauges. Relative sea level data are available from the National Oceanic and Atmospheric Administration, which publishes an interactive online map (http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml) with links to detailed data for each tide gauge.

Technical Documentation

Download related technical information PDF

References

1. Titus, J.G., E.K. Anderson, D.R. Cahoon, S. Gill, R.E. Thieler, and J.S. Williams. 2009. Coastal sensitivity to sea-level rise: A focus on the Mid-Atlantic region. U.S. Climate Change Science Program and the Subcommittee on Global Change Research. https://downloads.globalchange.gov/sap/sap4-1/sap4-1-final-report-all.pdf.

2. University of Colorado at Boulder. 2016. Sea level change: 2016 release #2—trend map. Accessed June 2016. http://sealevel.colorado.edu.

3. CSIRO (Commonwealth Scientific and Industrial Research Organisation). 2015 update to data originally published in: Church, J.A., and N.J. White. 2011. Sea-level rise from the late 19th to the early 21st century. Surv. Geophys. 32:585–602. www.cmar.csiro.au/sealevel/sl_data_cmar.html.

4. NOAA (National Oceanic and Atmospheric Administration). 2016. Laboratory for Satellite Altimetry: Sea level rise. Accessed June 2016. www.star.nesdis.noaa.gov/sod/lsa/SeaLevelRise/LSA_SLR_timeseries_global.php.

5. NOAA (National Oceanic and Atmospheric Administration). 2016 update to data originally published in: NOAA. 2009. Sea level variations of the United States 1854–2006. NOAA Technical Report NOS CO-OPS 053. www.tidesandcurrents.noaa.gov/publications/Tech_rpt_53.pdf.

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Oceans

Ocean Heat

Sea Surface Temperature

Sea Level

A Closer Look: Land Loss Along the Atlantic Coast

Coastal Flooding

Ocean Acidity

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Climate Change Indicators: Marine Species Distribution

This indicator examines changes in the location of fish, shellfish, and other marine species along U.S. coasts.

Figure 1. Change in Latitude and Depth of Marine Species, 1982â€“2015

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This graph shows the annual change in latitude (movement in miles) and depth (feet) of 105 marine species along the Northeast coast and in the eastern Bering Sea. Changes in the centers of biomass have been aggregated across all 105 species.

Data source: NOAA and Rutgers University, 20162
Web update: AugustÂ 2016

Figure 2. Average Location of Three Fish and Shellfish Species in the Northeast, 1968â€“2015

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					<fieldset id="species-map-series-2"><legend>Species</legend>

<input type="checkbox" value="american-lobster" />American lobster

<input type="checkbox" value="red-hake" />Red hake

<input type="checkbox" value="black-sea-bass" />Black sea bass

					</fieldset>

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This map shows the annual centers of biomass for three species in the northeastern United States from 1968 to 2015. Dots are shaded from light to dark to show change over time.

Data source: NOAA and Rutgers University, 20163
Web update: AugustÂ 2016

Figure 3. Average Location of Three Fish and Shellfish Species in the Bering Sea, 1982â€“2015

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					<fieldset id="species-map-series-3"><legend>Species</legend>

<input type="checkbox" value="alaska-pollock" />Alaska pollock

<input type="checkbox" value="snow-crab" />Snow crab

<input type="checkbox" value="pacific-halibut" />Pacific halibut

					</fieldset>

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This map shows the annual centers of biomass for three species in the eastern Bering Sea from 1982 to 2015. Dots are shaded from light to dark to show change over time.

Data source: NOAA and Rutgers University, 20164
Web update: AugustÂ 2016

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Figure 1. Change in Latitude and Depth of Marine Species, 1982â€“2015

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Figure 2. Average Location of Three Fish and Shellfish Species in the Northeast, 1968â€“2015

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Figure 3. Average Location of Three Fish and Shellfish Species in the Bering Sea, 1982â€“2015

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			Key Points

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			Background

About the

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			Indicator Notes

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Technical

			Documentation

Key Points

The average center of biomass for 105 marine fish and invertebrate species shifted northward by about 10 miles between 1982 and 2015 (see Figure 1). These species also moved an average of 20 feet deeper.

In waters off the northeastern United States, several economically important species have shifted northward since the late 1960s (see Figure 2). The three species shown in Figure 2 (American lobster, red hake, and black sea bass) have moved northward by an average of 119 miles.

In the Bering Sea, Alaska Pollock, snow crab, and Pacific halibut have generally shifted away from the coast since the early 1980s (see Figure 3). They have also moved northward by an average of 14 miles.

Background

Changes in water temperature can affect the environments where fish, shellfish, and other marine species live. Certain fish species naturally migrate in response to seasonal temperature changes, moving northward or to deeper, cooler waters in the summer and migrating back during the winter. As climate change causes the oceans to become warmer year-round (see the Ocean Heat and Sea Surface Temperature indicators), however, populations of some species may adapt by shifting away from areas that have become too warm and toward areas that were previously cooler. Along U.S. coasts, this means a shift northward or to deeper waters that may have a more suitable temperature. As smaller prey species shift their habitats, larger predator species may follow them.

Marine species represent a particularly good indicator of warming oceans because they are sensitive to climate and because they have been studied and tracked for many years. Fish are especially mobile, and they may shift their location more easily than species on land because they face fewer physical barriers.1 Also, many marine species, especially fish, do not have fixed nesting places or dwellings that might otherwise compel them to stay in one place. Populations of many marine species have been measured consistently for several decades across various types of ocean habitats. Tracking data from many species is useful because if a change in behavior or distribution occurs across a large range of species, it is more likely the result of a more systematic or common cause.

About the Indicator

This indicator tracks marine animal species in terms of their â€œcenter of biomass,â€? which is a point on the map that represents the center of each speciesâ€™ distribution by weight. If a fish population were to shift generally northward, the center of biomass would shift northward as well. This approach is similar to the way changes in bird population distributions have been measured (see the Bird Wintering Ranges indicator).

Data for this indicator were collected by the National Oceanic and Atmospheric Administrationâ€™s National Marine Fisheries Service and other agencies. These agencies monitor marine species populations by conducting annual surveys in which they trawl the ocean at regular intervals along the coast. By recording what they catch at each location, scientists can calculate each speciesâ€™ center of biomass in terms of latitude, longitude, and depth.

This indicator focuses on two survey regions that have the most continuous and longest-running sampling: the Northeast and the eastern Bering Sea off the coast of Alaska. Figure 1 shows the average change in the center of biomass across 105 species in these regions. For consistency, Figure 1 is limited to species that were identified every year. Figures 2 and 3 show detailed changes for three species in each region. These species were chosen because they represent a variety of habitats and species types (a mixture of fish and shellfish) and because they tend to be fairly abundant. Some of these species support major fisheries, yet are presumed to not be heavily impacted by overfishing, reducing the chance that fishing is unduly influencing the observed trends. Northeast data come from surveys that have been conducted every spring since 1968, while Bering Sea data come from summer surveys that have been conducted consistently since 1982.

Indicator Notes

Water temperature is not the only factor that can cause marine animal populations to shift. Other factors could include interactions with other species, harvesting, ocean circulation patterns, habitat change, and speciesâ€™ ability to disperse and adapt. As a result, species might have moved northward for reasons other than, or in addition to, changing sea temperatures. This indicator is limited to the Northeast and the eastern Bering Sea because these areas have used consistent survey methods and because they do not have coastlines that would prevent species from moving northward in response to warming (in contrast to regions like the Gulf of Mexico, where the coast blocks northward migration).

Data Sources

Data for this indicator were collected by the National Oceanic and Atmospheric Administrationâ€™s National Marine Fisheries Service during annual bottom trawl fisheries surveys. These data have been processed and made publicly available by Rutgers University at: http://oceanadapt.rutgers.edu. Data from these surveys have been used to support a wide variety of studies.5

Technical Documentation

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References

1 Pinsky, M.L., B. Worm, M.J. Fogarty, J.L. Sarmiento, and S.A. Levin. 2013. Marine taxa track local climate velocities. Science 341:1239â€“1242.

2 NOAA (National Oceanic and Atmospheric Administration) and Rutgers University. 2016. OceanAdapt. http://oceanadapt.rutgers.edu.

3Â NOAA (National Oceanic and Atmospheric Administration) and Rutgers University. 2016. OceanAdapt. http://oceanadapt.rutgers.edu.

4 NOAA (National Oceanic and Atmospheric Administration) and Rutgers University. 2016. OceanAdapt. http://oceanadapt.rutgers.edu.

5Â Pinsky, M.L., B. Worm, M.J. Fogarty, J.L. Sarmiento, and S.A. Levin. 2013. Marine taxa track local climate velocities. Science 341:1239â€“1242.

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Tribal Connection: Trends in Stream Temperature in the Snake River

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Downloads for the Indicators Report

The information on this website is drawn from the fourth edition of EPA's Climate Change Indicators in the United States, published in 2016. This report presents 37 indicators, each describing trends related to the causes and effects of climate change. It focuses primarily on the United States, but in some cases global trends are presented to provide context or a basis for comparison. The online version is updated periodically as new data become available, and thus may differ from the printed version available below.

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Climate Change Indicators: Heat-Related Deaths

This indicator presents data on deaths classified as â€œheat-relatedâ€? in the United States.

Figure 1. Deaths Classified as â€œHeat-Relatedâ€? in the United States, 1979â€“2014

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This figure shows the annual rates for deaths classified as â€œheat-relatedâ€? by medical professionals in the 50 states and the District of Columbia. The orange line shows deaths for which heat was listed as the main (underlying) cause.* The blue line shows deaths for which heat was listed as either the underlying or contributing cause of death during the months from May to September, based on a broader set of data that became available in 1999.

* Between 1998 and 1999, the World Health Organization revised the international codes used to classify causes of death. As a result, data from earlier than 1999 cannot easily be compared with data from 1999 and later.

Data source: CDC, 20169,10
Web update: AugustÂ 2016

Figure 2. Summer Deaths Due to Heat and Cardiovascular Disease in the United States, 1999â€“2014

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This figure shows rates for deaths that medical professionals have classified as being caused by a combination of cardiovascular disease (diseases of the circulatory system) and heat exposure. This graph presents summer (May to September) death rates from 1999 to 2014 for three population groups in the 50 states and the District of Columbia. The purple line shows rates for the entire population, the green line shows rates for non-Hispanic black people, and the pink line shows rates for people aged 65 and older.

Data source: CDC, 201611
Web update: AugustÂ 2016

Example: Examining Heat-Related Deaths During the 1995 Chicago Heat Wave*

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Many factors can influence the nature, extent, and timing of health consequences associated with extreme heat events.12Â Studies of heat waves are one way to better understand health impacts, but different methods can lead to very different estimates of heat-related deaths. For example, during a severe heat wave that hit Chicago* between July 11 and July 27, 1995, 465 heat-related deaths were recorded on death certificates in Cook County.13Â However, studies that compared the total number of deaths during this heat wave (regardless of the recorded cause of death) with the long-term average of daily deaths found that the heat wave likely led to about 700 more deaths than would otherwise have been expected.14Â Differences in estimated heat-related deaths that result from different methods may be even larger when considering the entire nation and longer time periods.

* This graph shows data for the Chicago Standard Metropolitan Statistical Area.

Data sources: CDC, 2012;15Â NOAA, 201216
Web update: AugustÂ 2016

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Figure 1. Deaths Classified as â€œHeat-Relatedâ€? in the United States, 1979â€“2014

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Figure 2. Summer Deaths Due to Heat and Cardiovascular Disease in the United States, 1999â€“2014

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Example: Examining Heat-Related Deaths During the 1995 Chicago Heat Wave*

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Key Points

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Background

About the
Indicator

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Indicator Notes

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Data Sources

Technical
Documentation

Key Points

Between 1979 and 2014, the death rate as a direct result of exposure to heat (underlying cause of death) generally hovered around 0.5 to 1 deaths per million people, with spikes in certain years (see Figure 1). Overall, a total of more than 9,000 Americans have died from heat-related causes since 1979, according to death certificates.

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For years in which the two records overlap (1999â€“2014), accounting for those additional deaths in which heat was listed as a contributing factor results in a higher death rateâ€”nearly double for some yearsâ€”compared with the estimate that only includes deaths where heat was listed as the underlying cause (see Figure 1).

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The indicator shows a peak in heat-related deaths in 2006, a year that was associated with widespread heat waves and was one of the hottest years on record in the contiguous 48 states (see the U.S. and Global Temperature indicator).

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The death rate from heat-related cardiovascular disease ranged from 0.08 deaths per million people in 2004 to 1.08 deaths per million people in 1999 (see Figure 2). Overall, the interaction of heat and cardiovascular disease caused about one-fourth of the heat-related deaths recorded in the â€œunderlying and contributing causesâ€? analysis since 1999 (see Figures 1 and 2).

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Since 1999, people aged 65+ have been several times more likely to die from heat-related cardiovascular disease than the general population, while non-Hispanic blacks generally have had higher-than-average rates (see Figure 2).

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Examination of extreme events has revealed challenges in capturing the full extent of â€œheat-relatedâ€? deaths. For example, studies of the 1995 heat wave event in Chicago (see example figure) suggest that there may have been hundreds more deaths than were actually reported as â€œheat-relatedâ€? on death certificates.

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While dramatic increases in heat-related deaths are closely associated with the occurrence of hot temperatures and heat waves, these deaths may not be reported as â€œheat-relatedâ€? on death certificates. This limitation, as well as considerable year-to-year variability in the data, make it difficult to determine whether the United States has experienced a meaningful increase or decrease in deaths classified as â€œheat-relatedâ€? over time.

Background

When people are exposed to extreme heat, they can suffer from potentially deadly illnesses, such as heat exhaustion and heat stroke. Hot temperatures can also contribute to deaths from heart attacks, strokes, and other forms of cardiovascular disease. Heat is the leading weather-related killer in the United States, even though most heat-related deaths are preventable through outreach and intervention (see EPAâ€™s Excessive Heat Events Guidebook at: www.epa.gov/heat-islands/excessive-heat-events-guidebook).

Unusually hot summer temperatures have become more common across the contiguous 48 states in recent decades1 (see the High and Low Temperatures indicator), and extreme heat events (heat waves) are expected to become longer, more frequent, and more intense in the future.2 As a result, the risk of heat-related deaths and illness is also expected to increase.3 Reductions in cold-related deaths are projected to be smaller than increases in heat-related deaths in most regions.4 Death rates can also change, however, as people acclimate to higher temperatures and as communities strengthen their heat response plans and take other steps to continue to adapt.

Certain population groups already face higher risks of heat-related death, and increases in summertime temperature variability will increase that risk.5,6 The population of adults aged 65 and older, which is expected to continue to grow, has a higher-than-average risk of heat-related death. Children are particularly vulnerable to heat-related illness and death, as their bodies are less able to adapt to heat than adults, and they must rely on others to help keep them safe.7 People with certain diseases, such as cardiovascular and respiratory illnesses, are especially vulnerable to excessive heat exposure, as are the economically disadvantaged. Data also suggest a higher risk among non-Hispanic blacks.8

About the Indicator

This indicator shows the annual rate for deaths classified by medical professionals as â€œheat-relatedâ€? in the United States based on death certificate records. Every death is recorded on a death certificate, where a medical professional identifies the main cause of death (also known as the underlying cause), along with other conditions that contributed to the death. These causes are classified using a set of standard codes. Dividing the annual number of deaths by the U.S. population in that year, then multiplying by one million, will result in the death rates (per million people) that this indicator shows.

Figure 1 shows heat-related death rates using two methods. One method shows deaths for which excessive natural heat was stated as the underlying cause of death from 1979 to 2014. The other data series shows deaths for which heat was listed as either the underlying cause or a contributing cause, based on a broader set of data that, at present, can only be evaluated back to 1999. For example, in a case where cardiovascular disease was determined to be the underlying cause of death, heat could be listed as a contributing factor because it can make the individual more susceptible to the effects of this disease. Because excessive heat events are associated with summer months, the 1999â€“2014 analysis was limited to May through September.

Figure 2 offers a closer look at cardiovascular disease deaths for which heat was recorded as a contributing cause. This graph includes deaths due to heart attacks, strokes, and other diseases related to the circulatory system. Figure 2 shows death rates for the overall population as well as two groups with a higher risk: people age 65 and older and non-Hispanic blacks. Like the â€œunderlying and contributing causesâ€? analysis in Figure 1, Figure 2 is restricted to the summer months, and it uses data that are available from 1999 to 2014.Â

Indicator Notes

Several factors influence the ability of this indicator to estimate the true number of deaths associated with extreme heat events. It has been well documented that many deaths associated with extreme heat are not identified as such by the medical examiner and might not be correctly coded on the death certificate. In many cases, the medical examiner might classify the cause of death as a cardiovascular or respiratory disease, not knowing for certain whether heat was a contributing factor, particularly if the death did not occur during a well-publicized heat wave. Furthermore, deaths can occur from exposure to heat (either as an underlying cause or as a contributing factor) that is not classified as extreme and therefore is often not recorded as such. Some statistical approaches estimate that more than 1,300 deaths per year in the United States are due to extreme heat, compared with about 600 deaths per year in the â€œunderlying and contributing causesâ€? data set shown in Figure 1.17 By studying how daily death rates vary with temperature in selected cities, scientists have found that extreme heat contributes to far more deaths than the official death certificates might suggest.18 This is because the stress of a hot day can increase the chance of dying from a heart attack, other heart conditions, or respiratory diseases such as pneumonia.19 These causes of death are much more common than heat-related illnesses such as heat stroke. Thus, this indicator very likely underestimates the number of deaths caused by exposure to heat.

Classifying a death as â€œheat-relatedâ€? does not mean that high temperatures were the only factor that caused or contributed to the death, as pre-existing medical conditions can significantly increase an individualâ€™s susceptibility to heat. Other important factors, such as the overall vulnerability of the population, the extent to which people have adapted and acclimated to higher temperatures, and the local climate and topography, can affect trends in heat-related deaths. Heat response measures, such as early warning and surveillance systems, air conditioning, health care, public education, cooling centers, infrastructure standards, and air quality management, can also make a big difference in reducing death rates. For example, after a 1995 heat wave, the city of Milwaukee developed a plan for responding to extreme heat conditions; during a 1999 heat wave, heat-related deaths were roughly half of what would have been expected.20

Future development related to this indicator should focus on capturing all heat-related deaths, not just those with a reported link to heat stress.

Data Sources

Data for this indicator were provided by the U.S. Centers for Disease Control and Prevention (CDC). The 1979â€“2014 underlying cause data in Figure 1 are publicly available through the CDC WONDER database at: http://wonder.cdc.gov/mortSQL.html. The 1999â€“2014 analysis in Figure 1 was developed by CDCâ€™s Environmental Public Health Tracking Program, which provides a summary at: www.cdc.gov/nceh/tracking. The cardiovascular disease data in Figure 2 are publicly available through the CDC WONDER database at: http://wonder.cdc.gov/mcd-icd10.html.

Technical Documentation

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References

1Â Melillo, J.M., T.C. Richmond, and G.W. Yohe (eds.). 2014. Climate change impacts in the United States: The third National Climate Assessment. U.S. Global Change Research Program. http://nca2014.globalchange.gov.

2 Melillo, J.M., T.C. Richmond, and G.W. Yohe (eds.). 2014. Climate change impacts in the United States: The third National Climate Assessment. U.S. Global Change Research Program. http://nca2014.globalchange.gov.

3 IPCC (Intergovernmental Panel on Climate Change). 2014. Climate change 2014: Impacts, adaptation, and vulnerability. Working Group II contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge University Press. www.ipcc.ch/report/ar5/wg2.

4 Sarofim, M.C., S. Saha, M.D. Hawkins, D.M. Mills, J. Hess, R. Horton, P. Kinney, J. Schwartz, and A. St. Juliana. 2016. Chapter 2: Temperature-related death and illness.Â The impacts of climate change on human health in the United States: A scientific assessment. U.S. Global Change Research Program. https://health2016.globalchange.gov.

5 Zanobetti, A., M.S. Oâ€™Neill, C.J. Gronlund, and J.D. Schwartz. 2012. Summer temperature variability and long-term survival among elderly people with chronic disease. P Natl. Acad. Sci. USA 109(17):6608â€“6613.

6 Sarofim, M.C., S. Saha, M.D. Hawkins, D.M. Mills, J. Hess, R. Horton, P. Kinney, J. Schwartz, and A. St. Juliana. 2016. Chapter 2: Temperature-related death and illness.Â The impacts of climate change on human health in the United States: A scientific assessment. U.S. Global Change Research Program. https://health2016.globalchange.gov.

7 USGCRP, 2016:Â The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. Crimmins, A., J. Balbus, J.L. Gamble, C.B. Beard, J.E. Bell, D. Dodgen, R.J. Eisen, N. Fann, M.D. Hawkins, S.C. Herring, L. Jantarasami, D.M. Mills, S. Saha, M.C. Sarofim, J. Trtanj, and L. Ziska, Eds. U.S. Global Change Research Program, Washington, DC, 312 pp.Â Â http://dx.doi.org/10.7930/J0R49NQX

8 Berko, J., D.D. Ingram, S. Saha, and J.D. Parker. 2014. Deaths attributed to heat, cold, and other weather events in the United States, 2006â€“2010. National Health Statistics Reports, Number 76. National Center for Health Statistics. www.cdc.gov/nchs/data/nhsr/nhsr076.pdf.

9 CDC (U.S. Centers for Disease Control and Prevention). 2016. CDC WONDER database: Compressed mortality file, underlying cause of death. Accessed February 2016. http://wonder.cdc.gov/mortSQL.html.

10 CDC (U.S. Centers for Disease Control and Prevention). 2016. Indicator: Heat-related mortality. National Center for Health Statistics. Annual national totals provided by National Center for Environmental Health staff in June 2016. http://ephtracking.cdc.gov/showIndicatorPages.action.

11 CDC (U.S. Centers for Disease Control and Prevention). 2016. CDC WONDER database: Multiple cause of death file. Accessed July 2016. http://wonder.cdc.gov/mcd-icd10.html.

12 Anderson, G.B., and M.L. Bell. 2011. Heat waves in the United States: Mortality risk during heat waves and effect modification by heat wave characteristics in 43 U.S. communities. Environ. Health Persp. 119(2):210â€“218.

13 CDC (U.S. Centers for Disease Control and Prevention). 1995. Heat-related mortalityâ€”Chicago, July 1995. Morbidity and Mortality Weekly Report 44(31):577â€“579.

14 NRC (National Research Council). 2011. Climate stabilization targets: Emissions, concentrations, and impacts over decades to millennia. Washington, D.C.: National Academies Press.

15 CDC (U.S. Centers for Disease Control and Prevention). 2012. CDC WONDER database. Accessed August 2012. http://wonder.cdc.gov/mortSQL.html.

16 NOAA (National Oceanic and Atmospheric Administration). 2012. National Centers for Environmental Information. Accessed August 2012. www.ncdc.noaa.gov.

17 Sarofim, M.C., S. Saha, M.D. Hawkins, D.M. Mills, J. Hess, R. Horton, P. Kinney, J. Schwartz, and A. St. Juliana. 2016. Chapter 2: Temperature-related death and illness.Â The impacts of climate change on human health in the United States: A scientific assessment. U.S. Global Change Research Program. https://health2016.globalchange.gov.

18 Medina-RamÃ³n, M., and J. Schwartz. 2007. Temperature, temperature extremes, and mortality: A study of acclimatization and effect modification in 50 U.S. cities. Occup. Environ. Med. 64(12):827â€“833.

19 Kaiser, R., A. Le Tertre, J. Schwartz, C.A. Gotway, W.R. Daley, and C.H. Rubin. 2007. The effect of the 1995 heat wave in Chicago on all-cause and cause-specific mortality. Am. J. Public Health 97(Supplement 1):S158â€“S162.

20 Weisskopf, M.G., H.A. Anderson, S. Foldy, L.P. Hanrahan, K. Blair, T.J. Torok, and P.D. Rumm. 2002. Heat wave morbidity and mortality, Milwaukee, Wis., 1999 vs. 1995: An improved response? Am. J. Public Health 92:830â€“833.

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Climate Change Indicators: Snow and Ice

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Community Connection:

The Earth’s surface contains many forms of snow and ice, including sea, lake, and river ice; snow cover; glaciers, ice caps, and ice sheets; and frozen ground. Climate change can dramatically alter the Earth’s snow- and ice-covered areas because snow and ice can easily change between solid and liquid states in response to relatively minor changes in temperature. This chapter focuses on trends in snow, glaciers, and the freezing and thawing of oceans and lakes.

Why does it matter?

Reduced snowfall and less snow cover on the ground could diminish the beneficial insulating effects of snow for vegetation and wildlife, while also affecting water supplies, transportation, cultural practices, travel, and recreation for millions of people. For communities in Arctic regions, reduced sea ice could increase coastal erosion and exposure to storms, threatening homes and property, while thawing ground could damage roads and buildings and accelerate erosion. Conversely, reduced snow and ice could present commercial opportunities for others, including ice-free shipping lanes and increased access to natural resources.

Such changing climate conditions can have worldwide implications because snow and ice influence air temperatures, sea level, ocean currents, and storm patterns. For example, melting ice sheets on Greenland and Antarctica add fresh water to the ocean, increasing sea level and possibly changing ocean circulation that is driven by differences in temperature and salinity. Because of their light color, snow and ice also reflect more sunlight than open water or bare ground, so a reduction in snow cover and ice causes the Earth’s surface to absorb more energy from the sun and become warmer.

Summary of Key Points

Arctic Sea Ice. Part of the Arctic Ocean is covered by ice year-round. The area covered by ice is typically smallest in September, after the summer melting season. The annual minimum extent of Arctic sea ice has decreased over time, and in September 2012 it was the smallest ever recorded. The length of the melt season for Arctic ice has grown, and the ice has also become thinner, which makes it more vulnerable to further melting.

Antarctic Sea Ice. Antarctic sea ice extent in September and February has increased somewhat over time. The September maximum extent reached the highest level on record in 2014—about 7 percent larger than the 1981–2010 average. Slight increases in Antarctic sea ice are outweighed by the loss of sea ice in the Arctic during the same time period, however.

Glaciers. Glaciers in the United States and around the world have generally shrunk since the 1960s, and the rate at which glaciers are melting has accelerated over the last decade. The loss of ice from glaciers has contributed to the observed rise in sea level.

Lake Ice. Lakes in the northern United States are freezing later and thawing earlier compared with the 1800s and early 1900s. Freeze dates have shifted later at a rate of roughly half a day to one-and-a-half days per decade. All of the lakes studied were also found to be thawing earlier in the year, with spring thaw dates growing earlier by up to 24 days in the past 110 years.

Community Connection: Ice Breakup in Two Alaskan Rivers. Regions in the far north are warming more quickly than other parts of the world. Two long-running contests on the Tanana and Yukon rivers in Alaska—where people guess the date when the river ice will break up in the spring—provide a century’s worth of evidence revealing that the ice on these rivers is generally breaking up earlier in the spring than it once did.

Snowfall. Total snowfall—the amount of snow that falls in a particular location—has decreased in most parts of the country since widespread records began in 1930. One reason for this decline is that nearly 80 percent of the locations studied have seen more winter precipitation fall in the form of rain instead of snow.

Snow Cover. Snow cover refers to the area of land that is covered by snow at any given time. Between 1972 and 2015, the average portion of North America covered by snow decreased at a rate of about 3,300 square miles per year, based on weekly measurements taken throughout the year. There has been much year-to-year variability, however. The length of time when snow covers the ground has become shorter by nearly two weeks since 1972, on average.

Snowpack. The depth of snow on the ground (snowpack) in early spring decreased at more than 90 percent of measurement sites in the western United States between 1955 and 2016. Across all sites, snowpack depth declined by an average of 23 percent during this time period.

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Climate Change Indicators

Climate Change Indicators: Sea Surface Temperature

This indicator describes global trends in sea surface temperature.

Figure 1. Average Global Sea Surface Temperature, 1880â€“2015

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This graph shows how the average surface temperature of the worldâ€™s oceans has changed since 1880. This graph uses the 1971 to 2000 average as a baseline for depicting change. Choosing a different baseline period would not change the shape of the data over time. The shaded band shows the range of uncertainty in the data, based on the number of measurements collected and the precision of the methods used.

Data source: NOAA, 20166
Web update: August 2016

Figure 2. Change in Sea Surface Temperature, 1901â€“2015

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This map shows how average sea surface temperatureÂ around the world changed between 1901 and 2015. It is based on a combination of direct measurements and satellite measurements. A blackÂ â€œ+â€? 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, 20137; NOAA, 20168
Web update: AugustÂ 2016

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Figure 1. Average Global Sea Surface Temperature, 1880â€“2015

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Figure 2. Change in Sea Surface Temperature, 1901â€“2015

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			Key Points

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			Background

About the

			Indicator

Â

			Indicator Notes

Â

			Data Sources

Technical

			Documentation

Key Points

Sea surface temperature increased during the 20th century and continues to rise. From 1901 through 2015, temperatureÂ rose at an average rate of 0.13Â°F per decade (see Figure 1).

Sea surface temperatureÂ hasÂ been consistently higher during the past three decades than at any other time since reliable observations began in 1880 (see Figure 1).

Based on the historical record, 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 temperatureÂ appears to have cooled between 1880 and 1910 (see Figure 1).

Changes in sea surface temperature vary regionally. While most parts of the worldâ€™s oceans have seen temperatureÂ rise, a few areas have actually experienced coolingâ€”for example, parts of the North Atlantic (see Figure 2).

Background

Sea surface temperatureâ€”the temperature of the water at the ocean surfaceâ€”is an important physical attribute of the worldâ€™s oceans. The surface temperature of the worldâ€™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 temperatureÂ increases and the ocean circulation patterns that transport warm and cold water around the globe 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 â€œred tide.â€?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.3Â 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 shift storm tracks, potentially contributing to droughts in some areas.4 Increases in sea surface temperatureÂ are also expected to lengthen the growth season for certain bacteria that can contaminate seafood and cause foodborne illnesses, thereby increasing the risk of health effects.5

About the Indicator

This indicator tracks average global sea surface temperature from 1880 through 2015. It also includes a map to show how change in sea surface temperature has varied across the worldâ€™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 developed by the Intergovernmental Panel on Climate Change, which calculated long-term trends based on a collection of published studies.

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.

Data Sources

Data for Figure 1 were provided by the National Oceanic and Atmospheric Administrationâ€™s National Centers for Environmental Information and are available online at: www.ncdc.noaa.gov/data-access/marineocean-data/extended-reconstructed-sea-surface-temperature-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 is an updated version of a map that appeared in the Intergovernmental Panel on Climate Changeâ€™s Fifth Assessment Report (www.ipcc.ch/report/ar5/wg1), which gathered data from a variety of studies that provide the best available information about climate change.

Technical Documentation

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References

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):5297â€“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):352â€“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/wg1.

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/wg1.

5. Trtanj, J., L. Jantarasami, J. Brunkard, T. Collier, J. Jacobs, E. Lipp, S. McLellan, S. Moore, H. Paerl, J. Ravenscroft, M. Sengco, and J. Thurston. 2016. Chapter 6: Climate impacts on water-related illness. The impacts of climate change on human health in the United States: A scientific assessment. U.S. Global Change Research Program. https://health2016.globalchange.gov.

6. NOAA (National Oceanic and Atmospheric Administration). 2016. Extended reconstructed sea surface temperature (ERSST.v4). National Centers for Environmental Information. Accessed March 2016. www.ncdc.noaa.gov/data-access/marineocean-data/extended-reconstructed-sea-surface-temperature-ersst.

7. 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/wg1.

8. NOAA (National Oceanic and Atmospheric Administration). 2016. NOAA Merged Land Ocean Global Surface Temperature Analysis (NOAAGlobalTemp): Global gridded 5Â° x 5Â° data. National Centers for Environmental Information. Accessed June 2016. www.ncdc.noaa.gov/data-access/marineocean-data/noaa-global-surface-temperature-noaaglobaltemp.

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