3.3 Explaining & Predicting Climate Change Chapter 3: Changing Climate

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)

Fluctuating Climate If the pattern of repeated glaciation continues, Alberta will experience its next glaciation in the next 100 000 years There are many theories that try to explain these repeated cold periods

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

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

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

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

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

Shape of Earth’s Orbit (eccentricity) It is known to change every 100 000 years Sometimes it is quite circular and at other times it is elliptical as it is now

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 40 000 years

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

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%)

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

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.

Could Global Warming Cause Global Cooling?