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Climate Change

Climate Change. SND2D0. Climate Change. Has the climate in Southern Ontario always been the same? The same temperature? The same amount of precipitation? The same types of life? No! Climate changes, and has for as long as we are able to tell

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Climate Change

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  1. Climate Change SND2D0

  2. Climate Change • Has the climate in Southern Ontario always been the same? • The same temperature? • The same amount of precipitation? • The same types of life? • No! • Climate changes, and has for as long as we are able to tell • Some changes occur over a long time period while some occur very quickly in response to events on Earth

  3. Long-Term Changes • Long-Term changes • Changes in climate that are the result of slow processes • These changes include things like: • Continental Drift • Changes in Earth’s rotation

  4. Continental Drift • The Theory of Plate Tectonics • Says that Earth’s crust is composed of a series of plates floating on top of the liquid mantle • These plates are constantly (but slowly) shifting with respect to one another • This causes the landforms on the Earth’s crust to move relative to one another • The continents end up drifting apart/closer

  5. Plates

  6. Pangaea • In the Permian period (225 million years ago) all the continents were combined • Called Pangaea • Slowly over time they drifted apart from one another

  7. Climate Change? • Continents drifting causes changes in climate • Ocean and air currents change when continents move apart • Mountains are formed at converging plates • Land masses move to different hemispheres • The Northern hemisphere contains the most land mass • As a consequence it has the coldest winters and warmest summers • Water has a moderating effect on temperature (lake effect) • In the Permian however, the distribution of land was different

  8. Climate Cycles and Ice-Ages • Global temperatures have fluctuated throughout history • Sometimes the average temp drops so low that a large portion of the water on Earth freezes • These times are called ice-ages • The last one occurred ~ 20 000 years ago

  9. Ice-Ages • Earth’s climate cycles between ice-ages and interglacial period • Ice-ages have low temp. and a high proportion of glaciers • Interglacial periods have high temp.

  10. Beringia Land Bridge • During an ice-age, the sea level drops, exposing new land • Beringia land bridge • This land bridge was responsible for human migration into the Americas

  11. Why do Ice-Ages Occur? • Ice-ages occur due to shifts in the orbit of the Earth • Eccentricity: Change in the shape of Earths orbit • Tilt: Change in the angle of Earth’s axis • Precession: Change in the direction of the axis of Earth • These three changes add-up to large scale changes in global temperature • Differences in the amount of incoming light

  12. Eccentricity • The Earth’s orbit changes from roughly circular to more elliptical • This cycles every ~100,000 years • Is due to the gravitational influence of Jupiter and Saturn on Earth

  13. Tilt • The axis of the Earth is tilted with respect to the ecliptic plane • The plane of the planets’ orbits in the solar system • Earth’s axis is tilted 23.5º • This tilt changes from 22.1º – 24.5º • This cycles every 41 000 years • As the tilt changes, the angle that light hits the Earth changes

  14. Ecliptic Plane

  15. Precession • As the Earth spins, the axis wobbles • Just like a spinning top • This cycles every 26 000 years • Changes the seasons • This also changes the identity of the North Star • It is currently Polaris • 5000 ya it was Thuban • In 1000 years it will be Airai

  16. Precession – North Star

  17. Short-Term Climate Change • Some events cause very rapid changes in climate • Volcanic Eruptions • El Niño • Changes in Sun’s Radiation • Volcanic Eruptions • Volcanoes spew rocks, dust, and gases (like SO2) into the atmosphere • These things reflect a lot of the Sun’s light back into space • This cools the Earth • Eg: 1815, Mount Tambora in Indonesia erupted leading to a year “with no summer”

  18. Volcanic Eruptions

  19. El Niño • El Niño is a recurring weather pattern in the pacific ocean • Every 3-7 years the prevailing winds change direction • This alters the ocean currents • Instead of pushing warm water west, it gets pushed east towards South America

  20. Weather Changes • East Asia -Drought, cooler air, fewer cyclones • Mid-pacific – warmer air/water, more cyclones

  21. La Niña • La Niña • The cooling period between El Niño episodes

  22. La Niña • La Niña • The cooling period between El Niño episodes

  23. La Niña

  24. Homework • Pg 353 # 1 – 8

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