Transcript What factors can cause climate change? Studying Climate Change

Long Term Changes in
Climate
Chapter 14 Section 3
Essential Questions Ch14 S3
1. What principle do scientists
follow in studying ancient
climates?
2. What changes occur on Earth’s
surface during an ice age?
3. What factors can cause
climate change?
Studying Climate Change
In studying ancient climates,
scientists follow an important
principle: If plants or animals
today need certain conditions
to live, then similar plants and
animals in the past also
required those conditions.
Scientists study ancient
climates to find out how
climates have changed during
the history of Earth. Changes in
climate may have affected
many regions around the world.
When scientists study ancient
climates, they assume that the
ancestors of today’s plants needed
the same conditions to live. For
example, if a palm tree needs a hot
and rainy climate to live today,
scientists assume that palm trees
long ago also needed hot and rainy
climates.
One source of information
about ancient climates is
pollen. Pollen is made by
plants. Scientists find pollen in
plant material at the bottoms of
some lakes.
Another source of information
about ancient climates is tree
rings. A tree ring forms every
year a tree grows. The size of
the ring depends on how much
the tree grows.
Ice
Age
Ice Age
During each ice age, huge sheets
of ice called glaciers covered
large parts of Earth’s surface.
An ice age is a period in Earth’s
history when glaciers covered
large parts of Earth. Over
millions of years, warm periods
have alternated with ice ages.
Scientists think we are now in a
warm period between ice ages.
Ice ages can last 100,000 years
or more. The last ice age ended
about 10,500 years ago. When
that ice age ended, the ice
melted and the Great Lakes
formed
Causes of Climate Change
Possible explanations for major
climate changes include variations
in the position of Earth relative to
the sun, changes in the sun’s
energy output, major volcanic
eruptions, and the movement of
continents.
Over thousands of years,
Earth’s orbit around the sun
shifts a little. The tilt of Earth’s
axis also changes slightly. The
combined effects of these
changes may be the main cause
of ice ages.
Sunspots are dark, cooler
regions on the surface of the
sun. When there are many
sunspots, Earth’s temperature
may increase.
When volcanoes erupt, they
release gases and ashes into the
atmosphere. These materials
can block sunlight. As a result,
huge volcanic eruptions may
lower Earth’s temperatures.
About 225 million years ago,
there was a single continent on
Earth called Pangaea (pan JEE
uh). Pangaea broke apart, and
the continents have been
moving ever since. As the
continents have moved,
climates have changed
Essential Questions Ch14 S3
1. What principle do scientists follow in
studying ancient climates?
It a condition is needed to survive now
similar conditions were needed long
ago.
2. What changes occur on Earth’s surface
during an ice age?
The surface is covered in ice.
3. What factors can cause climate
change?
Variation in the Earth’s position, change
in the sun’s energy output, major
volcanic eruptions, & movement of the
continents