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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
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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