Transcript 3.0ClimateControls09

What Causes Different Climates?
Presentation Outline:
Map of
World
Climates
I.
Significance of climate
II.
Global climate controls
III. Short-term climate changes
IV. Long term climate change
V.
Human-caused climate change
I. The Significance of Climate
A. What is the difference between climate and
weather?
1. Climate: the average, year after year
conditions of temperature and precipitation in a
particular region
2. Weather: the condition of the atmosphere at a
certain time and place
Powered by the sun, the climate system is a
complex exchange of energy and moisture among
Earth’s atmosphere.
II. Global Climate Controls
Latitude
Elevation
Topography
Water Bodies
Atmospheric Circulation
Vegetation
A. Latitude
1. Because the Earth tilts on its axis, and because the
earth is spherical the Sun’s rays strike the Earth at
different angles.
a. as a result, different parts of Earth receive
different amounts of solar radiation.
Compare area #1 to area #3.
Notice in area #3 the given amount
of light (and heat) is spread over a
larger area, so the energy is less
concentrated.
3. The tropics receive the
most solar radiation
because the sun’s rays
strike almost directly.
Temperatures in the
tropics are warm yearround.
4. The temperate zones have
moderate conditions.
5. The polar zones receive the
least radiation because the
sun’s rays strike at a very
low angle. Temperatures
in polar regions are usually
cold.
B. Elevation
1. Elevation is the height above sea level.
2. On average, air temperature drops about
6.5ºC for every 1000 m of altitude.
3. The higher the elevation, the colder the climate
4. Elevation determines the amount of precipitation.
-higher elevation typically means increased
precipitation
C. Topography
1. Climates often differ on either side of a mountain.
2. As air rises over a mountain, it cools. As it cools,
it condenses, and releases moisture (rain). This is
called the windward side.
3. As the dry air flows over the mountain, it
descends and warms, usually producing deserts.
This is called the leeward side.
Deserts such
as the
Atacama in
Chile are
common on
leeward
sides of
mountains.
The dry area is
Called a rain shadow and
can extend for hundreds
of km downwind of a
mountain range
D. Water Bodies
1. Land gains and loses heat much faster than water.
2. The temperature of a large body of water can
influence the temperature of the air above it.
3. Based on other factors certain areas closer to large
bodies of water may have a relatively small yearly
temperature range.
a. example: the California coast vs. the north-eastern
seaboard of the U.S.A.
4. Continental interiors have large yearly temperature
ranges.
Water Bodies (Continued)
1. Ocean currents can warm or cool the air above.
2. Ocean currents may be considerably warmer or
colder than the normal air temperature for that
latitude.
E. Atmospheric Circulation
1. There are three basic wind systems in each
hemisphere: Polar Easterlies, Northeast or Southeast
Tradewinds and Prevailing Westerlies.
2. These winds blow air masses with distinct regions of
origin (ie. formed over land or water, formed at certain
latitudes).
3. Winds move warm air toward the poles and cool air
toward the equator.
F. Vegetation
1. Vegetation influences how much of the sun’s energy is
absorbed and how quickly this energy is released, which
affects the climate.
2. During transpiration, plants release water vapor
from their leaves into the air.
3. Some plants release particles that promote the
formation of clouds.
III. Short Term Natural Climate Changes
A. Changes in climate trends, measured in months to years
1. Seasons
•
The tilt of the earth’s axis causes different
areas of Earth to receive different amounts of
solar radiation
•
This results in variations in daylight,
temperature and weather patterns
•
When the north pole is pointed toward the
sun, the northern hemisphere experiences
summer and the southern hemisphere
experiences winter (A)
•
During spring and fall, neither pole points
toward the sun (B)
2. Volcanic Activity
•
Volcanic dust can remain suspended in the atmosphere
for several years
•
This blocks incoming solar radiation and lowers global
temperatures
1991 eruption of Mt. Pinatubo
1980 eruption of Mt. Saint Helens
3. El Niño
•
Caused by a warm ocean current that occasionally develops off
the west coast of South America- due to shift in wind patterns
•
Negative Effects of El Nino:
•

Wet, stormy weather occurs in areas that are normally dry

Drought conditions occur in areas that are normally wet

Violent storms brought to California and the Gulf Coast

Extensive property damage and untold human suffering
Positive Effects of El Nino:

Fewer and less severe hurricanes in the Atlantic ocean
regions
Video- El Niño Consequences
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
CNN 2003
Normal Conditions
El Niño Conditions
Pacific Ocean
Pacific Ocean
Normal:
cool dry
climate
Due to winds,
Waters are warm
in W. Pacific
The cool dry
climate
becomes warm
and wet!
Cold water is
transported north from
Antarctica.
Antarctica
Westerly trade
winds weaken
and warm water
flows east
IV. Long Term Natural Climate Changes
A. Changes in climate trends, measured over tens to hundreds of
thousands of years
1. Ice Ages
•
Glaciers have alternatively advanced and retreated over
the past 2 million years
•
Ice Ages are periods of extensive glacial coverage
•
Global temperatures drop 5 degrees Celsius on average
•
Most recent Ice Age ended 10,000 years ago
2. Earth’s Orbit
•
Every 100,000 years, the shape of Earth’s orbit changes,
becoming more elliptical, then more circular
•
When the orbit elongates, earth passes closer to the sun
and temperatures become warmer than normal
•
When the orbit is more circular, temperatures dip below
average
3. Earth’s Axis
•
The angle of tilt varies from 22.1º to 24.5º every 41,000 years
•
Changes in angle cause seasons to become more severe
•
A decreased tilt might cause winters to be warmer than
normal and summers to be cooler than normal
•
Changes in tilt may be responsible for Ice Ages
4. Earth’s Wobble
•
Over a period of 26,000 years, Earth wobbles as it spins on
its axis
•
Currently the axis points toward the North Star (Polaris) and
winter occurs in the northern hemisphere when Earth is
closest to the sun
•
When the axis tilts toward Vega, winter will occur in the
northern hemisphere when Earth is farthest from the sun

This will cause warmer summers and colder winters than
those we now experience
V. Human-Influenced Climate Change
Global Warming
From epa.gov [2009]:
“For over the past 200 years, the burning of fossil fuels, such as coal
and oil, and deforestation have caused the concentrations of heattrapping ‘greenhouse gases’ to increase significantly in our
atmosphere. These gases prevent heat from escaping to space,
somewhat like the glass panels of a greenhouse.”
YOU will share more details about this issue with the class in a
PRESENTATION!
Here is an animation of one of the potential impacts of global
warming from the Center for Remote Sensing of Ice Sheets and their data on Sea Level rise
at: https://www.cresis.ku.edu/research/data/sea_level_rise/index.html