1. Long and Short Term Changes in Climate

2. Natural events such as volcanic eruptions
Long Term Changes
Movement of Earth’s Crust
Cyclical changes from warmer to colder climates due to variations in Earth’s orbit
Short Term Changes
Natural events such as volcanic eruptions

3. Long-Term Changes Due to Continental Drift
According to the theory of Plate Tectonics, Earth’s continents have moved over the surface of the globe for hundreds of millions of years  called continental drift
There use to be a supercontinent called Pangaea

4. Continental Drift Video Questions
What mountain ranges formed from the collision of India and Asia?
How do you think Antarctica’s change in position affected its climate?
Which ocean formed in the division between North America and Europe?

5. Long-Term Changes Due to Continental Drift
When continents move, the effect on climate includes:
Ocean and wind patterns change, affecting heat transfer
Distribution of land mass changes
Example: Canada (Northern Hemisphere with fewer large bodies of water)  coldest winters and warmest summers)
Uplifts new mountain ranges affects local and regional climate

6. Long-Term Cycles in Climate
It is believed that the earth’s climate cycles between ices ages and interglacial periods
Ice Age: a time in Earth’s history when Earth was colder and much of the planet is covered in ice
Interglacial period: time between ice ages, when the Earth warms up

7. Interglacial Period
About 20,000 years ago, the earth experienced its last ice age. The average temperature was 10°C lower than today.
Ice sheets about 3 km thick covered much of Canada.
Today, we are in an interglacial (warming) period.
Frequency of warm interglacial periods: about every 100,000 years

9. Why do Interglacial and Ice Ages happen?
The earth’s orbit around the sun changes in 3 main ways:
1. Eccentricity: shape of orbit around the Sun
Varies from being circular to being more elliptical
Influenced by Jupiter’s and Saturn’s gravities
Cycles every 100,000 years 

11. Why do Interglacial and Ice Ages happen?
2. Tilt (Affects seasons)
Varies from 22.1° to 24.5°
Cycles every 41,000 years
Currently the tilt is 23.5° and slowly decreasing

12. Why do Interglacial and Ice Ages happen?
3. Precession of Tilt
As Earth spins on its axis, it slowly wobbles in a cycle over 26,000 years

14. Short-Term Variations in Climate
Small variations in climate over tens of years to hundreds of years
Caused by volcanic eruptions, changes in the Sun’s radiation, and changes in the circulation of air and ocean currents

15. Short-Term Variations in Climate
Volcanic Eruptions
Spew rocks, dust and gases into the atmosphere
Sulfur dioxide (SO2) reflects the sun and earth temporarily cools down

16. Mt. Tambora Eruption Questions
How many years ago did Mt. Tambora erupt? Where did it erupt?
Which gas released from volcanic eruptions forms a reflective veil in the atmosphere?
What effect did the eruption of Mt. Tambora have on the Earth’s climate in the years following?

17. Short-Term Variations in Climate
Small Changes in the Sun’s radiation
The amount of solar radiation changes in small amounts over about 11 year cycles
We are currently in a solar minimum

18. Short-term Variations in Climate
Air and Ocean Currents
Changes in the ocean’s thermohaline circulation may cause abrupt changes in climate  phenomenon is not fully understood

19. Short-term Variations in Climate
Air and Ocean Currents
Changes in the ocean’s thermohaline circulation may cause abrupt changes in climate  phenomenon is not fully understood

20. Short-Term Changes in Climate
A dramatic change takes place in the Pacific Ocean every three to seven years
El Nino: periodic shift in Pacific winds and ocean currents; west coast of South America receives warmer, wetter weather

21. Homework
Note #10:
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