Long and short term changes in climate

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