Climate Change Causes for AS students

1. Are they Human or Natural? Are they Cooling or Warming? Causes of climate change

2. The earth’s rotation and orbit As the earth orbits the sun, it wobbles slightly on its axis. These “wobbles” are named after Milankovitch who discovered them. In the past the Milankovitch cycles have coincided with ice ages. http://www.wwnorton.com/college/geo/egeo/flash/18_2.swf Natural Human Cooling Warming

3. El Nino Occurs in the Pacific Ocean, where the normal circulation slows, stops and reverses. This causes the surface of the ocean to become warmer and causes significant changes in the weather patterns around the Pacific and globally Natural Human Cooling Warming

4. Ice albedo effect Ice and snow (being white) reflect incoming solar radiation. Albedo means reflectivity. Where there is a lot of ice it reflects enough energy to reduce global temperature http://svs.gsfc.nasa.gov/vis/a010000/a010000/a010021/a010021_H264_640x480.mp4 Natural Human Cooling Warming

5. Deforestation of Tropical Rainforests Tropical rainforest is a natural carbon sink (it absorbs a massive amount of carbon from the atmosphere), reducing CO2 levels. Evaporation from the Tropical Rainforest is very high and this causes clouds to form which reflect the sun’s energy When the rainforest is removed less CO2 is absorbed and less clouds form. Natural Human Cooling Warming

6. Fossil fuel burning Burning fossil fuels releases large quantities of CO2 into the atmosphere causing the enhanced greenhouse effect. Natural Human Cooling Warming

7. Deforestation of boreal (conifer) forest (in Siberia and Northern Canada) When forest is cleared in the far north it increases the albedo (reflectivity) of the earth because the forest is dark in colour and snow stays longer on the ground Natural Human Cooling Warming

8. Volcanic activity Large volcanic eruptions create huge quantities of particles which encircle the earth in the upper atmosphere. These reflect radiation and shade the earth for up to 5 years. Natural Human Cooling Warming

9. La Nina Occurs after El Nino. The Pacific circulation restarts, stronger than usual, this means that the surface waters have less time exposed to the sun, and to warm up. The ocean surface is cooler. Natural Human Cooling Warming