Transcript Ch. 24.7: Climate - Ramsey Public School District

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
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
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)
19
Ice Ages - Cause
55 Ma: Uplift of the Himalayas
4. Changes in continental arrangements
Can change ocean currents or air flow 
can change climate
Uplift of new land  more weathering 
cooling
Ice Ages: Cause
5. Change in Thermohaline Circulation
(melting sea ice changes salinity of
water; no sinking = slow down of THC)
 change climate.
Ancient Ice Age: Snow Ball Earth
Ice covered Earth ~
2.4 bya (end of
Precambrian Time)
Global temps: ~ - 74 F
6. Biology Driven Ice Age = Snowball Earth
Weaker sun (30% weaker) + Arrival of
photosynthesizing bacteria (removing CO2 from
atmosphere) = ICE
•ICE has high albedo --> more solar radiation reflected -->
less energy absorbed --> MORE ICE
•Volcanic GHG eventually warm planet up