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Transcript
Section 14.3
Climatic Changes
Objectives
Distinguish between long-term and shortterm climatic changes.
Identify natural causes of climate change.
Recognize why climatic changes occur.
Section 14.3
Climatic Changes
Earth’s climate is constantly changing on
many different timescales.
Review Vocabulary
glacier: large, moving mass of ice that forms
near Earth’s poles and in mountainous
regions at high elevations
Section 14.3
Climatic Changes
New Vocabulary
ice age
El Niño
season
Maunder minimum
Section 14.3
Climatic Changes
Long-Term Climatic Changes
Ice ages
During the periods of extensive glacial
coverage called ice ages, average global
temperatures decreased by an estimated
5°C.
most recent ice age ended about 10,000
years ago.
an ice age may last for several million
years.
Section 14.3
Climatic Changes
Long-Term Climatic Changes
Ice ages
The most recent ice age, as
shown here by the extent of
its glaciers, ended only
about 10,000 years ago.
Section 14.3
Climatic Changes
Short-Term Climatic Changes- 2 categories
1.Seasons, 2.El Nino.
Seasons are due to Earth’s tilt on its axis
and revolution around the Sun which
leads to regular variations in daylight,
temperature, and weather patterns.
Section 14.3
Climatic Changes
Short-Term Climatic Changes
Seasons
The variations that occur with seasons
are the result of changes in the amount
of solar radiation an area receives.
Section 14.3
Climatic Changes
Short-Term Climatic Changes
Seasons
When the north pole is pointed away from the
Sun, the northern hemisphere experiences
winter and the southern hemisphere
experiences summer. During spring and fall,
neither pole points toward the sun.
Section 14.3
Climatic Changes
Short-Term Climatic Changes
El Niño
Other short-term climatic changes include
those caused by El Niño, a warm ocean
current that occasionally develops off the
western coast of South America.
Section 14.3
Climatic Changes
Short-Term Climatic Changes
El Niño
Under normal conditions, trade winds and
ocean currents move warm water west
across the Pacific Ocean.
Section 14.3
Climatic Changes
Short-Term Climatic Changes
El Niño
During El Niño, warm water surges
back toward South America, changing
weather patterns.
Section 14.3
Climatic Changes
5 Natural Causes of Climatic Changes
1.Solar activity, 2.Earth’s orbit, 3. Earth’s tilt,
4 Earth’s wobble, 5. Volcanic activity.
Solar activity
The Maunder minimum is the term used to
describe the period of low numbers of sunspots,
from 1645 to 1716.
This period closely corresponds to an unusually
cold climatic episode called the Little Ice Age.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Solar activity
Studies indicate that increased
solar activity coincides with
warmer-than-normal sea
surface temperatures, while
periods of low solar activity,
such as the Maunder
minimum, coincide with colder
sea surface temperatures.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Earth’s orbit
Climatic changes might also be triggered
by changes in Earth’s axis and orbit.
The shape of Earth’s elliptical orbit appears
to change, becoming more elliptical, then
more circular, over the course of a
100,000-year cycle.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Earth’s orbit
Scientists hypothesize that a more elliptical
orbit around the Sun could produce
significant changes in Earth’s climate.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Earth’s tilt
At present, the angle of the tilt of Earth’s axis
is 23.5°. However, the angle of tilt varies
from a minimum of 22.1° to a maximum of
24.5° every 41,000 years.
Scientists theorize that these changes in
angle affect the differences in seasons.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Earth’s tilt
If the angle of the tilt
of Earth’s axis
decreased, there
would be less
temperature contrast
between summer
and winter.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Earth’s wobble
Over a period of about 26,000 years, Earth
wobbles as it spins around on its axis.
Currently, the axis points toward the North
Star, Polaris.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Earth’s wobble
Earth’s wobble determines
the timing of the seasons.
When the axis points
toward the star Vega in
13,000 years, the northern
hemisphere will experience
summer during the time
now associated with winter.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Volcanic activity
Climatic changes can also be triggered by the
immense quantities of dust-sized particles,
called aerosols, that are released into the
atmosphere during major volcanic eruptions.
Section 14.3
Climatic Changes
Natural Causes of Climatic Changes
Volcanic activity
Volcanic dust can remain suspended in the
atmosphere for several years, blocking
incoming solar radiation and thus lowering
global temperatures.
CH
Study Guide
Key Concepts
Section 14.3 Climatic
Changes
Earth’s climate is constantly
changing on many different timescales.
 Climate change can occur on a long-term or
short-term scale.
CH
Study Guide
Key Concepts
Section 14.3 Climatic
Changes
 Changes in solar activity have been
correlated with periods of climate change.
 Changes in Earth’s orbit, tilt, and wobble are
all associated with changes in climate.
CH
Climate
14.3 Section Questions
Volcanic eruptions can affect global climate.
a. true
b. false
CH
Climate
14.3 Section Questions
What was low during the Maunder minimum?
a. the amount of precipitation
b. the number of sunspots
c. the number of full moons
d. the amount of cloud cover
CH
Climate
14.3 Section Questions
How would an increase in the tilt of Earth’s axis
probably affect summer and winter temperatures
at high latitudes?
a. cooler summers and warmer winters
b. cooler summers and cooler winters
c. warmer summers and cooler winters
d. warmer summers and warmer winters
CH
Climate
Standardized Test
Practice
What happens during an El Niño?
Possible answer: During an El Niño, the trade
winds that normally blow from east to west
across the tropical Pacific weaken, and warm
surface water moves eastward across the
Pacific Ocean. These changes trigger shortterm climate changes in the Pacific region and
in some other parts of the world.