How Human Activity Affects Greenhouse Gases

What are Greenhouse GasesAny gas that has three or more atoms in its structure will act as a greenhouse gasExamples - CO2, H2O, CFC, CH4, but not O2 or N2

Deforestation/burning of fossil fuels

Both affect carbon dioxide levelsCO2 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 CO2

Deforestation/burning of fossil fuels

Carbon Cycle – sinks/reservoirs – oceansVegetation e.g. treesCarbonate rocks e.g. limestone /chalkSoilsAtmosphereFossil fuels (coal, oil, Natural gas)

Major CO2 Releases

Burning coal, oil, gasDeforestation

Burn treesRelease CO2Reduction of trees which absorb CO2 during photosynthesis

Major CO2 Releases

Motor vehicles exhaustsProduce CO2

Add 7 million tons every year to the atmosphere

Major CO2 Releases

2/3 – Burning Fossil Fuels1/3 – DeforestationCO2 causes 50% of global warming

Cattle farming/Rice fieldsMethaneProduced by anaerobic bacteriaFound in bogs, swamps, marshes, paddy (rice) fieldsDigestive systems of cows, sheep, and camels

Methane1.7ppm

Compared to CO2 ~400ppmAccounts for 15% of global warming25 times better than CO2 at absorbing infra red radiationIncreasing at a rate of 1% per yearMajor contributor = India (cows)

Nitrous oxide -NOx

Burning fossil fuelDenitrifying bacteria can convert nitrate fertilizers to nitrous oxides.

Nitrogen Cycle

Accounts for 6 % global warming/greenhouse effect

CFC’s - ChlorofluorocarbansSources

Propellants in aerosol cansCoolants in refrigeratorExpanders in plastic insulating foam

CFC’s Account for 22% of global warmingMontreal protocol

CFC’s banned but very long “residence time”

Water VaporVery important greenhouse gas but not significantly affected by man