Download Ch. 24.7: Climate

Climate & Climate Change
Objectives:
1. What factors affect climate?
2. What is El Nino & how does it work?
3. What causes ice ages?
4. How can scientists determine
climate changes of the past?
Climate = Long term weather of a region
Depends on temperature & precipitation
6 Climate Regions:
Tropical: Hot & wet or Hot w/ wet & dry seasons
Dry:
Desert
Temperate marine: humid w/ mild winters
Temperate continental: cold, snowy winters
Highlands: mt. regions, cool & wet
Polar: tundra & ice cap
Climate: Factors Affecting Temperature
1. Altitude: Cooler @ higher altitudes
2. Latitude:
– Cooler as you move away fr. equator.
– Same latitudes have similar temps (solar radiation)
3. Distance from bodies of water:
– Water moderates temps.  less variation
• Landlocked areas – more extreme temps. (Hotter
summers & colder winters)
4. Ocean currents can influence temps.
Warm current  milder winters (Gulf stream brings warmer temps
to UK)
Cold current  cooler summers (California current brings cooler
summer to San Francisco)
Climate: Factors Affecting Precipitation.
1. Latitude
Tropical air holds more moisture  rainy
2. Distribution of air pressure systems & global winds
a. High Pressure Areas  Dry sinking air (30 N& S
and poles)
b. Low Pressure Areas  Moist rising air (0 & 60
degrees)
c. Global Winds
Wind from sea: Carry moist air  Wet climate
Wind from land: Dry Climate
3. Mt. Barriers
Mts. Force warm moist air from sea up 
condenses & precips. on one side of Mt. Dry on
other side
Mt. Barriers (Orogenic Uplift)
WINDWARD SIDE
LEEWARD
•Warm air is pushed
up by mountain,
condenses, &
precipitaties
•Dry Air on opposite
side
•WET
•Desert - like
Mountain Barriers && Climate
Cascade Mts.
Mountain Barriers &
Climate (Orogenic
Uplift)
Note how the western side of the
Cascade Mts. (windward) are
green with vegetation. The
eastern side of the Cascades
(leeward) are brown – due to a
lack of vegetation (It’s dry on this
side of the mountain).
Global Pressure Systems & Climate
Low pressure latitudes: Rainy/snowy
High pressure latitudes: Dry
Global Ocean Currents
Warm currents (Gulf Stream): milder winters
Cold currents (California Current): cooler summers
CH. 24.7 Climate Change:
Seasonal: El Nino
Natural Short Range Change in Climate
http://video.nationalgeographic.com/video/el-nino
El Nino year
El Nino: Periodic warming of water in the
central & eastern Pacific Ocean (off coast of
Peru)
Normally this water is VERY COLD due to an upwelling from
the deep ocean.
• Warm water affects atmosphere above water & trade
winds slacken
• Ocean currents in Pacific weaken or
reverse direction
Result: Abnormal weather (Drought in S.West
US, Austrialia, and S.E Asia; Milder winter
Eastern US)
When: Every 8 yrs (average)
El Nino year
La Nina – cooler water
El Nino– Warmer water
La Nina = Opposite of El Nino
Year when the cold current off the
coast of S. America is “extra” cool.
Climate Change: What Causes
a Planet to Warm Up or Cool
Down?
14
Climate Change: Ice Ages
Naturally Occuring, Long
Term
Ice Age: Colder than usual & glaciers cover larger
portion of Earth’s surface as they advance fr. poles.
When:
4 major ice ages in last 2 million years
Last one ended 10, 000 yrs ago
Crash Course in The Little Ice Age https://www.youtube.com/watch?v=YF8AAJSTJoM
Scientific American: Hot Planet, Cold Comfort Planet
http://www.youtube.com/watch?v=TikUkmpWwBI
http://www.pbs.org/wgbh/nova/ice/chill.html
http://courses.missouristate.edu/EMantei/creativ
e/glg110/glaciers.html
HIGH
18O:16O
LOW
18O:16O
Icehouse vs.
Greenhouse
ICE HOUSE = Ice present @ poles
GREEN HOUSE= NO ice present @
poles
16
Causes of Ice Ages
1. Milankovitch Cycles =
Changes in incoming solar
radiation due to variations in
Earth’s orbit, tilt, or wobble.
A. Change in shape of E’s orbit
(How elliptical or circular our orbit is. Varies
from 0 – 6% elliptical; Now: 1.7% elliptical)
Cycle: 100 000 years
More elliptical = more variation in climate =
ice age
B. Changes in Tilt
Ranges from 22 – 24.5 degrees (Now 23.5
degrees)
More Tilt = more seasonal variation = ice age
Cycle: 41 000 yrs
www.atmo.arizona.edu/.../sec5/robust.html
C. Changes in Wobble (direction of axis).
N. Pole pointed toward or away from sun?
Cycle: 23, 000 years
Causes of Ice Ages continued
2. Volcanic Activity
Dust & ash can
cause cooling in
short term by
blocking solar
radiation (ice
age)
Volcanic gases
cause warming
over long term
(b/c they are
greenhouse
gases)
18
3. Changes in Solar
Radiation (solar cycles)
Few or no sunspots for prolonged periods correlate
with cold periods; Prolonged sunspot activity =
warming
19
4. Mt. Building Episodes
Uplift of the Himalayas, Alps, Rockies, Andies
Changes in continental arrangements
Can change ocean currents or air flow 
can change climate
Uplift of new land  more weathering 
cooling
5. Change in Patterns of Ocean
Circulation
Change ocean
currents =
change climate
Ex: Gulf Stream brings warm water/air to Northern Europe. If Gulf
Stream slows or stops; there will be an ice age in Northern Europe.
Gulf Stream can be slowed by adding freshwater from melting
glaciers off the coast of Greenland. Adding freshwater to the ocean
changes its salinity and density; Water won’t sink; This changes
the pattern of ocean ocean currents that bring warm water to cold
places.
6. Biology Driven Ice Age = Snowball Earth
Ice covered Earth ~
2.4 bya (end of
Precambrian Time)
Global temps: ~ - 74 F
Arrival of photosynthesizing bacteria (removing
CO2 from atmosphere) = ICE AGE known as
SNOWBALL EARTH (mass extinction at the end of
Precambrian time)