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Global Changes in the
Atmosphere
Chapter 14 Section 4
Essential Questions C14 S4
1. What events can cause short-term
climate change?
2. How might human activities be
affecting the temperature of Earth’s
atmosphere?
3. How have human activities affected
the ozone layer?
Short-Term Climate Change
El Niño and La Niña are short-term
changes in the tropical Pacific
Ocean caused by changes in
ocean surface currents and
prevailing winds
Short Term Climate Change
Changes in ocean currents
and winds can greatly
affect climate.
Short Term Climate Change
El Niño is a period of warm water that
occurs every few years in the Pacific
Ocean. The warm waters of El Niño
change the normal ocean currents along
the Pacific coast of South America. When
ocean currents change, it causes
weather patterns to change. El Niño can
bring heavy rains or droughts to other
parts of the world.
Short Term Climate Change
La Niña is a period of colder than
normal surface waters in the
Pacific Ocean. La Niña is the
opposite of El Niño. La Niña
brings cold winters and greater
precipitation to the Pacific
Northwest of the United States.
Global Warming
Many scientists have
hypothesized that human
activities that add greenhouse
gases to the atmosphere may be
warming Earth’s atmosphere.
Global Warming
Over the last 120 years, the
average temperature of the
troposphere has increased. The
gradual increase in the
temperature of the atmosphere
is called global warming.
Global Warming
Earth’s surface is heated by energy from
the sun. Some of the heat is radiated
back into space. Certain gases in the
atmosphere hold heat that is radiated
from Earth. The process by which the
gases trap heat energy is called the
greenhouse effect
Global Warming
The gases in the atmosphere
that trap heat energy are
called greenhouse gases.
Greenhouse gases include
carbon dioxide, water vapor,
and methane.
Global Warming
Human activities add carbon
dioxide to the atmosphere.
For example, burning wood,
coal, and oil adds carbon
dioxide to the air.
Global Warming
Adding carbon dioxide to the
air increases the
greenhouse effect.
Increasing the greenhouse
effect may be the cause of
global warming.
Ozone Depletion
Chemicals produced by
humans have been
damaging the ozone
layer.
Ozone Depletion
Ozone in the atmosphere blocks
ultraviolet radiation from the
sun. The loss of ozone means
more ultraviolet radiation
reaches Earth’s surface.
Ultraviolet radiation can cause
eye damage and skin cancer.
Ozone Depletion
In the 1970s, scientists
noticed a hole in the
ozone layer of the
atmosphere.
Holes in the Ozone from 1980 2001
Ozone Depletion
A major cause of the ozone hole is a
group of chemicals that were used
in air conditioners, refrigerators,
and spray cans. The chemicals are
called chlorofluorocarbons, or
CFCs. In the atmosphere, CFCs
break down ozone into oxygen
atoms.
Ozone Depletion
The United States and other
countries have cut down
use of CFCs. People will stop
using CFCs completely by
about 2010.
Essential Questions C14 S4
1. What events can cause short-term
climate change?
• El Nino & La Nina can cause short-term
climate changes.
2. How might human activities be affecting
the temperature of Earth’s atmosphere?
• We may be adding greenhouse gases such
as carbon dioxide to the atmosphere.
EQ Answers Continued
3. How have human activities affected the
ozone layer?
•
We have released CFCs into the
atmosphere that break ozone down into
oxygen. This has thinned the ozone layer
and reduced our protection from harmful
ultraviolet radiation.