1. 3.3 Explaining & Predicting Climate Change
Chapter 3: Changing Climate

2. Climate Change
Weather – state of the atmosphere in terms of variables such as temperature, cloud cover, precipitation and humidity for a particular place at a particular time
Climate – the average of daily and seasonal weather events that occur in a region over a long time (> 30 years)

3. Fluctuating Climate
If the pattern of repeated glaciation continues, Alberta will experience its next glaciation in the next years
There are many theories that try to explain these repeated cold periods

4. Possible Causes of Glaciation
Plate Tectonics
Global Conveyor Belt
Volcanic Activity
Milankovitch Theory
Variation in sunspots
Enhanced Greenhouse Effect

5. Plate Tectonics – continents must be positioned near the poles in order for continental ice sheets to form on land to cause glaciation. Movement of the plates also impact the boundaries of the ocean and ocean currents

6. Global Conveyor Belt – the system of ocean currents that circulates warm water away from the tropics near the ocean’s surface

7. Volcanic Activity – soot, ash, dust and carbon dioxide are thrown high into the air reducing the amount of solar radiation that can be received at Earth’s surface

8. Milankovitch Theory
The glaciations that have occurred during mayor cold periods seem to match changes in Earth’s orbit around the sun and the Earth’s rotation on its axis
Milankovitch found that Earth’s orbit varies in 3 ways which affects the amount of solar radiation that can be received by Earth’s surface
Shape of Earth’s orbit
Tilt of Earth’s axis of rotation
Wobble of the axis of rotation

9. Shape of Earth’s Orbit (eccentricity)
It is known to change every years
Sometimes it is quite circular and at other times it is elliptical as it is now

10. Tilt of the Axis of Rotation
Our planet is tilted on its axis
Currently it is about 23.5° but it is not always the case
It can vary up to 1.5° every years

11. Wobble of the Axis of Rotation
the trend in the direction of the Earth's axis of rotation relative to the fixed stars, with a period of roughly 23,000 years
This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis

12. Variation in Sunspots
Changes in the intensity of solar radiation seem to follow a regular pattern determined by the frequency of sunspots
During times of more sunspots additional energy is released by the sun
The difference in energy output is small (0.1% - 0.2%)

13. Enhanced Greenhouse Effect
Earth’s atmosphere contains gases, such as carbon dioxide and methane that trap heat near Earth’s surface
Without this natural insulating effect, Earth would be much colder than even the coldest ice age
In more recent times, there has been a sharp increase in the concentration of carbon dioxide in the atmosphere
The increase in carbon dioxide coincides with an exponential increase in the emissions of carbon dioxide since the Industrial Revolution

14. Enhanced Greenhouse Effect
The largest human-caused source of atmospheric carbon dioxide is the burning of fossil fuels
Many scientists believe this increase is enhancing Earth’s natural greenhouse effect, shown by a significant increase in the average temperature during the last century
This graphic of the global air temperature was posted by Phil Jones on behalf of the Climatic Research Unit, UK. The key reference used was Brohan, et al.

15. Could Global Warming Cause Global Cooling?