How Human Activity Affects Greenhouse Gases

What are Greenhouse Gases Any gas that has three or more atoms in its structure will act as a greenhouse gas Examples - CO 2, H 2 O, CFC, CH 4, but not O 2 or N 2

Deforestation/burning of fossil fuels Both affect carbon dioxide levels CO 2 contributes most to the greenhouse effect because of its quantity. CFC’s are a 100,000 times more effective as a greenhouse gas but theirquanitiy is very low in comparison to CO 2

Deforestation/burning of fossil fuels Carbon Cycle – sinks/reservoirs – oceans Vegetation e.g. trees Carbonate rocks e.g. limestone /chalk Soils Atmosphere Fossil fuels (coal, oil, Natural gas)

Major CO 2 Releases Burning coal, oil, gas Deforestation Burn trees Release CO2 Reduction of trees which absorb CO2 during photosynthesis

Major CO 2 Releases Motor vehicles exhausts Produce CO 2 Add 7 million tons every year to the atmosphere

Major CO 2 Releases 2/3 – Burning Fossil Fuels 1/3 – Deforestation CO 2 causes 50% of global warming

Cattle farming/Rice fields Methane Produced by anaerobic bacteria Found in bogs, swamps, marshes, paddy (rice) fields Digestive systems of cows, sheep, and camels

Methane 1.7ppm Compared to CO 2 ~400ppm Accounts for 15% of global warming 25 times better than CO 2 at absorbing infra red radiation Increasing at a rate of 1% per year Major contributor = India (cows)

Nitrous oxide -NO x Burning fossil fuel Denitrifying bacteria can convert nitrate fertilizers to nitrous oxides. Nitrogen Cycle Accounts for 6 % global warming/greenhouse effect

CFC’s - Chlorofluorocarbans Sources Propellants in aerosol cans Coolants in refrigerator Expanders in plastic insulating foam CFC’s Account for 22% of global warming Montreal protocol CFC’s banned but very long “residence time”

Water Vapor Very important greenhouse gas but not significantly affected by man