1. Greenhouse Gases
SNC2D

2. Greenhouse Gases
The principal greenhouse gases that trap infrared radiation in the atmosphere are:
Water vapour
Carbon dioxide
Methane
Chlorofluorocarbons (CFCs)
Ozone
Nitrous oxide

3. Sources
These can be produced by natural processes (e.g. carbon dioxide is a product of respiration) but are increasingly produced by human activities.

4. Sources
For this reason we differentiate the natural greenhouse effect from the anthropogenic greenhouse effect (the excess produced by human activities).

5. Fossil Fuels
The primary human activities that produce greenhouse gases are fossil fuel extraction and use.
Trucks carrying oil-laden sand in Fort McMurray, Alberta

6. Fossil Fuels
Fossil fuels (oil, coal, and natural gas) formed underground from the remains of once-living organisms.

7. Fossil Fuels
As they are extracted from the ground, they release methane and carbon dioxide, and as they are burned to produce energy, they release large amount of nitrous oxide and carbon dioxide.
The Nanticoke coal-burning plant on Lake Erie.

8. Fossil Fuels
A lot of fossil fuel use occurs where you would not expect, such as farming; e.g. modern industrial farming uses fertilizer synthesized from natural gas in a process that itself consumes energy.

9. History
The discovery that these gases absorbed infrared radiation dates to 1861.
Back in 1896, Nobel Prize winner Svante Arrhenius calculated that the world temperature would rise by 5-6oC if carbon dioxide levels were doubled.

10. Rising Concentrations
And carbon dioxide levels have been rising:
This famous graph is known as the Keeling curve.

11. The Annual Cycle
Carbon dioxide levels decrease during the spring and summer months because that is when the Northern Hemisphere (most of the world’s landmass) is experiencing growth in carbon-dioxide absorbing vegetation.

12. Sinks
Forests act as carbon sinks (mechanisms that remove carbon dioxide from the air).
A significant fraction of the increase in carbon dioxide can be attributed to deforestation.

13. Looking Back Into the Past
To show that the increases in greenhouse gases are unprecedented and significant, we can look back into the past by looking at layers of ice in Greenland and Antarctica.

14. Looking Back Into the Past

15. More Practice
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