T

he Earth’s climate is changing. Temperatures are rising, snow and rainfall patterns 

are shifting, and more extreme climate events—like heavy rainstorms and recordhigh temperatures—are already taking place. Scientists are highly confident that 

many of these observed changes can be linked to the levels of carbon dioxide and other 

greenhouse gases in our atmosphere, which have increased because of human activities.

EPA partners with more than 40 data contributors from various government agencies, 

academic institutions, and other organizations to compile a key set of indicators related to 

the causes and effects of climate change. All of the indicators are based on observations 

over time and consist of the best available peer-reviewed, publicly available data. Some 

indicators show trends that can be more directly linked to human-induced climate change 

than others. Together, these indicators present credible and compelling evidence that 

climate change is happening now in the United States and globally.

Climate Change Indicators in the United States

www.epa.gov/climate-indicators 

EPA 430-F-16-071

October 2016

Lower troposphere

Earth’s surface (measured by satellite)

UAH RSS

4

3

2

1

0

-1

-2

-3

1900 1910 1920 1930 1940 1950 1960

Year

Temperature anomaly (°F)

1970 1980 1990 2000 2010 2020

Data source: National Oceanic and Atmospheric Administration (NOAA), 2016. National Centers for Environmental 

Information. ww.ncei.noaa.gov.

WHAT’S HAPPENING 

A few key points:

• Atmospheric Concentrations 

of Greenhouse Gases: 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.

• U.S. and Global Temperature: 

Average temperatures have risen 

across the contiguous 48 states 

since 1901. Global temperatures 

show a similar trend, and all of the 

top 10 warmest years on record 

worldwide have occurred since 

1998.

• Coastal Flooding: Flooding is 

becoming more frequent along 

the U.S. coastline as sea level rises. 

Nearly every site measured has 

experienced an increase in coastal 

flooding since the 1950s. The rate 

is accelerating in many locations 

along the East and Gulf coasts.

• Snowpack: Snowpack in early 

spring has decreased at more 

than 90 percent of measurement 

sites in the western United States 

between 1955 and 2016.

• Heat-Related Deaths: Since 1979, 

more than 9,000 Americans were 

reported to have died as a direct 

result of heat-related illnesses 

such as heat stroke. However, 

considerable year-to-year 

variability and certain limitations 

of the underlying data make it 

difficult to determine whether the 

United States has experienced 

long-term trends in the number of 

deaths classified as “heat-related.”

• Marine Species Distribution: The 

average center of biomass for 

105 marine fish and invertebrate 

species along U.S. coasts shifted 

northward by about 10 miles 

between 1982 and 2015. These 

species also moved an average of 

20 feet deeper. 

USING THE INDICATORS

EPA’s indicators are designed to be a “go-to” resource for 

the public, scientists, analysts, decision-makers, educators, 

and others who can use climate change indicators as a tool 

for communication, environmental assessment, and informed 

decision-making. The indicators are available in several forms. 

The indicators can be found online at: www.epa.gov/climate-indicators, 

where they are updated as data become available, usually on an annual basis. 

A PDF of the 2016 report is available online; order a printed copy by emailing: 

climateindicators@epa.gov.

This indicator shows how annual average temperatures in the contiguous 48 states 

changed from 1901 to 2015, using the 1901–2000 average as a baseline.

Temperatures in the Contiguous 48 States, 1901–2015
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 

• Tropical Cyclone Activity

• River Flooding 

• Drought 

• A Closer Look: Temperature and Drought 

in the Southwest 

Oceans

• Ocean Heat 

• Sea Surface Temperature

• Sea Level 

• A Closer Look: Land Loss Along the 

Atlantic Coast 

• Coastal Flooding 

• Ocean Acidity

Snow and Ice 

• Arctic Sea Ice 

• Antarctic Sea Ice 

• Glaciers 

• Lake Ice 

• Community Connection: Ice Breakup in 

Two Alaskan Rivers 

• Snowfall 

• Snow Cover 

• Snowpack 

Health and Society

• Heat-Related Deaths 

• Heat-Related Illnesses 

• Heating and Cooling Degree Days 

• Lyme Disease 

• West Nile Virus 

• Length of Growing Season 

• Ragweed Pollen Season 

Ecosystems 

• 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.

ABOUT THE INDICATORS

EPA currently presents 37 indicators and five features that each highlight a specific 

region, data record, or area of interest. The indicators and features are organized into 

six chapters, shown to the right.

Each indicator on EPA’s website includes:

• Easy-to-understand graphs or maps depicting changes over time. 

• Background on how the indicator relates to climate change.

• Key points about what the indicator shows.

• A description of each data source used and how the indicator was developed.

• Transparent technical support documentation. 

• Web links to download high-resolution figures and data files. 

CLIMATE CHANGE INDICATORS AND HEALTH

The 2016 Indicators report includes a feature on 

how climate change can affect human health and 

what indicators can tell us about such climate/health 

interactions. For more information about climate and 

health connections, look for this symbol throughout 

the printed edition (available in PDF form online).

Some indicators feature interactive maps online. For 

example, the sea level map shown here can be clicked to 

show trends at specific locations. 

Subscribe to receive indicator updates at: www.epa.gov/climate-indicators.

INTERACTIVE

MAPS