1. The Anthropogenic Greenhouse Effect

2. Anthropogenic Greenhouse Effect
“The enhancement of the natural greenhouse effect due to human activity.”
The Problem:
The increase in greenhouse gas levels may trap more IR in the atmosphere, increasing the average global temperature.

3. Greenhouse Effect Comparison

4. Anthropogenic Greenhouse Gases
Humans have little effect on water vapour since it moves rapidly through the water cycle.
Humans are increasing the levels of:
- Carbon dioxide, CO2
- Methane, CH4
- Nitrous oxide , N2O
- Halocarbons
- Ground Level Ozone
These do NOT exist naturally.
They are additional GH gases added by humans.

5. Carbon Dioxide Sources: Combustion of fossil fuels.
Transportation, heating, generating electricity, etc.
Burning forests to clear land.
Cement making.

6. Methane Sources: Coal and natural gas processing.
Agriculture (manure).
Landfill sites (garbage).

7. Nitrous Oxide Sources: Combustion of fossil fuels.
Chemical fertilizers.
Manure and sewage.

8. Halocarbons
Synthetic compounds containing carbon and halogen elements (F, Cl, Br).
Used as cleaners, solvents, and coolants.
Includes CFCs (chlorofluorocarbons).

9. CFCs and the Ozone Layer
The ozone layer in the stratosphere absorbs harmful ultraviolet radiation: UV
ozone (O3) oxygen (O2)
UV rays can cause skin cancer and cataracts.
CFC’s act as a catalyst to speed up the breakdown of O3:
CFC

10. CFCs and the Ozone Layer
CFCs banned since 1989.
Replaced by other halocarbons... but ALL halocarbons also absorb IR radiation and act as greenhouse gases too!

11. Global Warming Potential (GWP)
A measure of the ability of gases to trap (absorb) IR radiation.
carbon dioxide (CO2) = 1 (least potent)
methane (CH4) = 25
nitrous oxide (N2O) = 298
hydrofluorocarbon (HFC) = 14,800

12. Why Focus on Carbon?
CO2 has a low GWP but it is the most abundant greenhouse gas.
It is also a greenhouse gas that humans directly impact on a large scale.
Fossil fuel use has increased exponentially since the 1800s.
Fossil fuel extraction and combustion also releases N2O and CH4.

13. Ground Level Ozone A major component of smog.
Produced by photochemical reactions between N2O and volatile organic compounds in the presence of sunlight. 13

14. Ground Level Ozone
Higher levels occur from May to September, between noon and early evening.
Very harmful to environment: damages plants and severe respiratory health problems in humans and other animals.
Cement making accounts for ~7% of world production of CO2 (data from 1995) 14 14