1. LONG AND SHORT TERM CHANGES IN CLIMATE

2. LONG TERM CHANGES Continental Drift When continents move, ocean currents and wind patterns change which affects heat transfer Also affects the distribution of land More ocean south of equator – more moderate climate New mountain ranges, weathering of old mountain rangers

3. CLIMATE CYCLES Earth’s climate cycles between freezing ice ages and warmer interglacial periods Earth’s last ice age was 20 000 years ago Average temp was 10 degrees less Ice sheets 3km thick covered most of Canada

4. WHY CLIMATE CYCLES? Earth’s orbit! Eccentricity: shape of the orbit varies from being circular to elliptical (cycles every 100,000 years) Tilt: rangers from 22.1 -24.5 degrees (cycle is every 41,000 years) Wobble: As Earth spins it wobbles on it’s axis, angle remains the same but direction changes

6. SHORT TERM VARIATIONS IN CLIMATE Volcanic Eruptions clouds cause shading and cool Earth Changes in Air and Ocean Currents El Nino – Air/Water in pacific ocean changes direction every 3-7 years https://www.youtube.com/watch?v=7FVZrw7bk1w Changes in Sun’s Radiation Small changes make a big difference in Earth’s temperature

7. FEEDBACK LOOPS AND CLIMATE (8.10)

8. FEEDBACK LOOP Positive Feedback Loop : the effect increases the original cause A small change can have a big effect! Negative Feedback Loop : the effect decreases the original cause

9. THE WATER VAPOUR FEEDBACK LOOP Heat  increase water vapour  increase heat (greenhouse gas) Cool  less water vapour  Earth cools down even more

10. THE ALBEDO EFFECT Albedo : the amount of radiation reflected by a surface Different surfaces have different albedos Ex: Ice and snow have high albedos grass and trees have low albedos Albedo Effect : Positive feedback loop between ice on Earth’s surface and Earth’s temperature Colder  more ice  more reflection  cools more Warmer  less ice  less reflection  heats up more Earth shifts from ice age to warm period fairly quickly because of this effect

12. HOMEWORK! Read pg. 348-357 Questions Pg. 353 #1, 4 Pg. 357 #1-4, 6, 7

13. How do we know what Past Climates Were Like?? Ice Cores – test air bubbles to determine make up of atmosphere, can also help determine temperature Tree Rings – the thicker the rings, the better the conditions (warm, wet) Coral Reefs – Add layers of growth each year, determine water temperature Rock – layers contain pollen or fossils Ocean Sediment – layers contain fossils Caves – dripping minerals solidify, grow faster in rainy weather