Presentation on theme: "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."— Presentation transcript:
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 Warm air is pushed up by mountain, condenses, & precipitaties WET LEEWARD Dry Air on opposite side Desert - like
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
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 http://www.pbs.org/wgbh/nova/ice/chill.html http://courses.missouristate.edu/EMantei/creativ e/glg110/glaciers.htmleativ e/glg110/glaciers.html Scientific American: Hot Planet, Cold Comfort Planet http://www.youtube.com/watch?v=TikUkmpWwBI
Icehouse vs. Greenhouse 16 ICE HOUSE = Ice present @ poles GREEN HOUSE= NO ice present @ poles HIGH 18O:16O LOW 18O:16O
www.atmo.arizona.edu/.../sec5/robust.html 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 C. Changes in Wobble (direction of axis). N. Pole pointed toward or away from sun? Cycle: 23, 000 years
18 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) 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.
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 Ancient Ice Age: Snow Ball Earth Ice covered Earth ~ 2.4 bya (end of Precambrian Time) Global temps: ~ - 74 F