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.
    United States
    Environmental Protection
                                    limate  Change  SciencePdctS
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    TJ                 i
    amount of greenhouse gases is necessary     HaatflJ^Wlg greenhouse gases are HOW
    for life to exist on Earth-they trap heat in      at record-high levels in the atmosphere
    the atmosphere, keeping the planet warm              j    i  ?            j j
    and in a  state of equilibrium. But this natural    compared with, the recent and distant past.
    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.
          The Link Between Greenhouse Gases and Temperature,
          — 380

          •B 360
                    Global Temperature  - Carbon Dioxide Concentration

320 1901-2000AverageTemperature

          Source: Carbon Dioxide Information Analysis Center.2010. and
          National Oceanic and Atmospheric Administration. 2010.
          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.

As the climate
continues to warm,
more changes are
expected to  occur
and many effects
will  become more
pronounced over
                                 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 (°F) 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 (0.24°F per decade) is almost double the
                                         rate of warming over the last 100 years (0.13°F per decade).
                                     The evidence of climate
                                     ch         '
ge exrenas wen
)nd increases
oba surface
eratures. It also
precipitation patterns.
Melting ice in the
Melting glaciers
around the world.
Increasing ocean
Rising sea level
around the world.

Acidification of
the oceans due to
elevated carbon
dioxide in the
Responses by plants
and animals, such as
shifting ranges.
Temperatures in the Lower 48 States,
1901-2009 trend: +1.25T- per century
1979-2009 trend: Surface: +5.05Tpercentury UAH:+4.00Tpercentury RSS:+3.49Tpercentury
2 I 1
™ il 171
£ I r fcl'*
i II li I ^ ilk IM
1 1
• •• Earth's surface Lowertroposphere(measuredbysatellite)
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Source: National Oceanic and Atmospheric Administration. 2010.
www. ncdc.

Since 1901, temperatures have risen across the lower 48 states at
an average rate of 0. 13 °F per decade j 1 . 3 °F per century! . Average
temperatures have risen more quickly since the late 1 970s.

                                 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 c imate 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 environmenta changes.
                                     Today, effects of c imate 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.
                                                             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