1. Ch. 24. 7: Climate & Climate Change Objectives: 1
Ch. 24.7: 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?

2. 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

3. Climate: Factors Affecting Temperature
1. Altitude: 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)

4. 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)
b. 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

5. Mt. Barriers (Orogenic Uplift)
WINDWARD SIDE
Warm air is pushed up by mountain, condenses, & precipitaties
WET
LEEWARD
Dry Air on opposite side
Desert - like

6. Cascade Mts. – Washington State

7. 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).

8. Global Pressure Systems Influence Climate

9. Global Ocean Currents
Gulf Stream Current – Circulates warmer tropical water north (Britian is warmer than it should be at its latitude)

10. CH. 24.7 Climate Change: Seasonal: El Nino Natural Short Range Change in Climate

11. El Nino year

12. 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
When: Every 8 yrs (average)

13. 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

15. Icehouse vs. Greenhouse
LOW
18O:16O
HIGH 18O:16O
Icehouse vs. Greenhouse
ICE HOUSE = Ice poles
GREEN HOUSE= NO ice 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 “eccentricity” of orbit
(How elliptical or circular our orbit is. Varies from 0 – 6% elliptical; Now: 1.7% elliptical)
Cycle: 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: yrs
C. Changes in Wobble (direction of axis). N. Pole pointed toward or away from sun? Cycle: 23, 000 years

17. 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. 55 Ma: Uplift of the Himalayas
Ice Ages - Cause
55 Ma: Uplift of the Himalayas
4. Changes in continental arrangements (Plate tectonics)  can change ocean currents or air flow  can change climate

20. Ice Ages: Cause
5. Change in Thermohaline Circulation (melting sea ice changes salinity of water; no sinking = slow down of THC)  change climate.

21. 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