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?

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) 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

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

Cascade Mts. – Washington State

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 Influence Climate

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

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 When: Every 8 yrs (average)

Climate Change: What Causes a Planet to Warm Up or Cool Down?

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 http://www.pbs.org/wgbh/nova/ice/chill.html http://courses.missouristate.edu/EMantei/creative/glg110/glaciers.html

Icehouse vs. Greenhouse LOW 18O:16O HIGH 18O:16O Icehouse vs. Greenhouse ICE HOUSE = Ice present @ poles GREEN HOUSE= NO ice present @ poles

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: 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 C. Changes in Wobble (direction of axis). N. Pole pointed toward or away from sun? Cycle: 23, 000 years www.atmo.arizona.edu/.../sec5/robust.html

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)

3. Changes in Solar Radiation (solar cycles)

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

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