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 & precipitation6 Climate Regions:Tropical: Hot & wet or Hot w/ wet & dry seasonsDry: DesertTemperate marine: humid w/ mild wintersTemperate continental: cold, snowy wintersHighlands: mt. regions, cool & wetPolar: tundra & ice cap
3 Climate: Factors Affecting Temperature 1. Altitude: higher altitudes2. 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 variationLandlocked 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. LatitudeTropical air holds more moisture rainy2. Distribution of air pressure systems & global windsa. High Pressure Areas Dry sinking air (30 N& S and poles)b. Low Pressure Areas Moist rising air (0 & 60 degrees)b. Global WindsWind from sea: Carry moist air Wet climateWind from land: Dry Climate3. Mt. BarriersMts. Force warm moist air from sea up condenses & precips. on one side of Mt. Dry on other side
5 Mt. Barriers (Orogenic Uplift) WINDWARD SIDEWarm air is pushed up by mountain, condenses, & precipitatiesWETLEEWARDDry Air on opposite sideDesert - like
7 Orogenic UpliftNote 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).
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 slackenOcean currents in Pacific weaken or reverse directionResult: Abnormal weatherWhen: 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 yearsLast one ended 10, 000 yrs ago
15 Icehouse vs. Greenhouse LOW18O:16OHIGH 18O:16OIcehouse vs. GreenhouseICE HOUSE = Ice polesGREEN HOUSE= NO ice poles
16 Causes of Ice Ages1. 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: yearsMore elliptical = more variation in climate = ice ageB. Changes in TiltRanges from 22 – 24.5 degrees (Now 23.5 degrees)More Tilt = more seasonal variation = ice ageCycle: yrsC. 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 ActivityDust & 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)
19 55 Ma: Uplift of the Himalayas Ice Ages - Cause55 Ma: Uplift of the Himalayas4. Changes in continental arrangements (Plate tectonics) can change ocean currents or air flow can change climate
20 Ice Ages: Cause5. 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 F6. Biology Driven Ice Age = Snowball EarthWeaker sun (30% weaker) + Arrival of photosynthesizing bacteria (removing CO2 from atmosphere) = ICEICE has high albedo --> more solar radiation reflected --> less energy absorbed --> MORE ICEVolcanic GHG eventually warm planet up