Transcript Climate part2

Sec. 14 - 3
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
I. Long-Term Climatic Changes
A. Ice ages
1. Glaciers advance and retreat
2. Average global temperatures
decreased by 5°C
3. Snowfall increased
B. Interglacial Intervals
1. Warm periods
between ice ages
2. The most recent
ice age ended
about 10,000 years
ago
II. Short-Term Climatic Changes
A. Seasons - caused by regular variations
in daylight, temperature, and
weather patterns
1. Changes in solar radiation
a. Tilt of Earth’s axis
b. Earth is a sphere
2. Opposite in N & S hemispheres
B. El Niño - warm ocean current that
occasionally develops off the western
coast of South America
Under normal conditions, trade winds and
ocean currents move warm water west across
the Pacific Ocean.
During El Niño, warm water surges back
toward South America, changing weather
patterns.
1. Warm water heats surrounding air and
convection current strengthen
a. NW South America becomes
warmer and wetter
2. Upper level winds move system east
a. Violent storms in CA and Gulf Coast
b. Storms where it’s usually dry
c. Drought where it’s usually wet
3. Strong Trade Winds
a. La Niña
b. South American coast
becomes colder
III. Natural Causes of Climatic Changes
A. 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.
Studies indicate that
increased solar activity
coincides with warmerthan-normal sea surface
temperatures, while
periods of low solar
activity, such as the
Maunder minimum,
coincide with colder sea
surface temperatures.
Figure 14.18 Page 390
B. Earth’s 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.
Fig. 14.19 Page 390
Scientists hypothesize that a more elliptical orbit around the Sun
could produce significant changes in Earth’s climate.
C. 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.
Fig. 14.20 Page 391
If the angle of the tilt of Earth’s axis decreased, there would be less
temperature contrast between summer and winter.
D. 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.
Fig. 14.21 Page 391
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.
E. Volcanic activity
1. Aerosols
a. dust-sized particles that are released during
major volcanic eruptions
b. Remain suspended for several years
c. blocking incoming solar radiation
d. lowers global temperatures
Sec. 14 - 4
Impact of Human Activities
Over time, human activities can alter
atmospheric conditions enough to
influence changes in weather and climate.
Review Vocabulary
radiation: transfer of thermal energy
by electromagnetic waves
I. Influence on the Atmosphere
A. The greenhouse effect
1. Natural heating of Earth’s surface caused by
certain atmospheric gases
2. Can lead to a rise in global temperatures,
known as global warming
Please click the image above to view the video.
II. Global Warming
Temperatures worldwide have shown an
upward trend over the past 200 years, with
several of the warmest years on record
having occurred within the last two
decades.
Fig. 14.24 Page 394
A. Burning fossil fuels
1. Main source of atmospheric carbon dioxide
2. Coal, oil, and natural gas
3. Also releases other greenhouse gases
a. methane
b. nitrous oxide
B. Deforestation
1. The mass removal of trees
2. Increases levels of atmospheric carbon dioxide
a. Photosynthesis is reduced
b. carbon dioxide remains in the atmosphere
C. Environmental efforts
Earth’s climate is constantly
changing on many different timescales.
 Climate change can occur on a longterm or short-term scale.
 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.
Over time, human activities can alter
atmospheric conditions enough to influence
changes in weather and climate.
 The greenhouse effect influences Earth’s
climate.
 Worldwide temperatures have shown an
upward trend over the past 200 years.
 Human activities can influence changes in
weather and climate.
 Individuals can reduce their environmental
impact on climate change.