Causes of Climate Change

Climate change is a term that refers to major changes in temperature, rainfall, snow, or wind patterns lasting 

for decades or longer. Both human-made and natural factors contribute to climate change:

• Human causes include burning fossil fuels, cutting down forests, and developing land for farms, cities, 

and roads. These activities all release greenhouse gases into the atmosphere.

• Natural causes include changes in the Earth’s orbit, the sun’s intensity, the circulation of the ocean and 

the atmosphere, and volcanic activity.

Although the Earth’s climate has changed many times throughout its history, the rapid warming seen today 

cannot be explained by natural processes alone.

Human activities are increasing the amount of 

greenhouse gases in the atmosphere. Some 

amount of greenhouse gases is necessary 

for life to exist on Earth—they trap heat in 

the atmosphere, keeping the planet warm 

and in a state of equilibrium. But this natural 

greenhouse effect is being strengthened as 

human activities (such as the combustion of 

fossil fuels) add more of these gases to the atmosphere, resulting in a shift in the Earth’s equilibrium.

Climate Change ScienceFacts

Climate change is 

a real and urgent 

challenge that is already 

affecting people and the 

environment worldwide. 

Significant changes are 

occurring on Earth, 

including increasing air 

and ocean temperatures, 

widespread melting of 

snow and ice, and rising 

sea levels. This fact sheet 

discusses key scientific 

facts that explain the 

causes and effects of 

climate change today, 

as well as projections for 

the future.

Office of Air and Radiation (6207J) 

EPA 430-F-10-002

www.epa.gov/climatechange 

April 2010 

Heat-trapping greenhouse gases are now 

at record-high levels in the atmosphere 

compared with the recent and distant past.

1850 1870 1890 1910 1930 1950 1970 1990 2010

260

280

300

320

340

360

380

400

Atmospheric Carbon Dioxide Concentration (ppm)

-1

-0.5

0

0.5

1

1.5

Temperature Difference from Baseline (°F)

Global Temperature Carbon Dioxide Concentration

1901-2000 Average Temperature

Year

The Link Between Greenhouse Gases and Temperature,

1850–2009

Emissions of carbon dioxide, an important greenhouse gas, have been increasing 

since the Industrial Revolution. These emissions are causing carbon dioxide levels to 

build up in the atmosphere and global temperatures to rise. In particular, temperatures 

have gone up at an increased rate over the past 30 years. Carbon dioxide data 

in this figure are compiled from several different studies. Temperature data show the 

difference from the average or baseline temperature between 1901 and 2000. 

Source: Carbon Dioxide Information Analysis Center. 2010. http://cdiac.ornl.gov/ and 

National Oceanic and Atmospheric Administration. 2010. www.noaa.gov
Signs of Climate Change

Climate change is happening now, and the effects can be seen on every continent and in every ocean. 

While certain effects of climate change can be beneficial, particularly in the short term, current and future 

effects of climate change pose considerable risks to people’s health and welfare, and the environment.

There is now clear evidence that the Earth’s climate is warming:

• Global surface temperatures have risen by 1.3 degrees Fahrenheit (oF) over the last 100 years. 

• Worldwide, the last decade has been the warmest on record. 

• The rate of warming across the globe over the last 50 years (0.24oF per decade) is almost double the 

rate of warming over the last 100 years (0.13oF per decade).

The evidence of climate 

change extends well 

beyond increases 

in global surface 

temperatures. It also 

includes:

• Changing 

precipitation patterns.

• Melting ice in the 

Arctic.

• Melting glaciers 

around the world.

• Increasing ocean 

temperatures.

• Rising sea level 

around the world.

• Acidification of 

the oceans due to 

elevated carbon 

dioxide in the 

atmosphere.

• Responses by plants 

and animals, such as 

shifting ranges.

Projections of Climate Change

At the current rate, the Earth’s global average temperature is projected to rise from 3 to 7°F by 2100, and 

it will get even warmer after that. As the climate continues to warm, more changes are expected to occur, 

and many effects will become more pronounced over time. For example, heat waves are expected to 

become more common, severe, and longer lasting. Some storms are likely to become stronger and more 

frequent, increasing the chances of flooding and damage in coastal communities.

Climate change will affect different regions, ecosystems, and sectors of the economy in many ways, 

depending not only on the sensitivity of those systems to climate change, but also on their ability to 

adapt to risks and changing conditions. Throughout history, societies and ecosystems alike have shown 

remarkable capacity to respond to risks and adapt to different climates and environmental changes. 

Today, effects of climate change have already been observed, and the rate of warming has increased in 

recent decades.

For this reason, human-caused climate change represents a serious challenge—one that could require new 

approaches and ways of thinking to ensure the continued health, welfare, and productivity of society and 

the natural environment. 

Year

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Temperature anomaly (°F)

-3

-2

-1

0

1

2

3 1901–2009 trend: +1.25°F per century

1979–2009 trend: Surface: +5.05°F per century UAH: +4.00°F per century RSS: +3.49°F per century

Earth's surface Lower troposphere (measured by satellite) 

 UAH RSS

Temperatures in the Lower 48 States,

1901–2009

Since 1901, temperatures have risen across the lower 48 states at 

an average rate of 0.13°F per decade (1.3°F per century). Average 

temperatures have risen more quickly since the late 1970s.

Source: National Oceanic and Atmospheric Administration. 2010. 

www.ncdc.noaa.gov/oa/ncdc.html

As the climate 

continues to warm, 

more changes are 

expected to occur 

and many effects 

will become more 

pronounced over 

time.

For More Information

For detailed information about greenhouse gas emissions, 

the effects of climate change, EPA efforts underway, 

and tips on what you can do, visit EPA’s Climate Change 

Web site at www.epa.gov/climatechange.