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Atmospheric Composition
Atmosphere is a thin layer of gas held to the planet by gravity.
composed of mainly nitrogen 78%, 21% oxygen, argon, and water.
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Radiative forcing
Change in net(down minus up) atmospheric radiation at the top of the troposphere.
amount that earth is out of energy balance.
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Greenhouse gasses increase longwave trapping by?
energy balance gets restored in outgoing longwave radiation through stefan boltzmann feedback.
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Radiative forcing facts:
- -GHG have positive radiative forcing
- -CO2 has the largest radiative forcing of the anthropogenic GHGs
- -Radiative forcing ΔTs= λΔF
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What determines effectiveness of a GHG?
- -concentration of gas in atmosphere
- -frequency os absorption band relative to blackbody spectrum for earth
- -lifetime
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Carbon Cycle changes
- -prior to the pre industrial revolution, a steady state was maintained.
- -carbon cycle was balanced such that the distribution of carbon between reservoirs was not undergoing large changes.
- -emission of CO2 by humans disrupted that balance
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Car emissions:
The amount of carbon released to the atmosphere has been increasing (1.9 ppmv/yr)
Anthropogenic emissions are 130x greater than volcanic emissions:
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Natural sources and anthropogenic sources of carbon emissions
- N = Forest fires, volcanic eruptions
- An = combustion of fossil fuels, deforestation
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Deforestation:
- -clearance of forests by logging and burning
- -releases C stored in above and below ground biomass and in soils
- -undisturbed forests hold 20-50 x more C than ecosystems that replace them
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Forests cover what percent of land surface
30%
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Deforestation resultants
- -13 million hectares per year, equivalent to area of costa rica.
- -20-25% of GHG emissions more than transportation emissions.
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Fossil Fuel Combustion:
burning of fossilized organic matter to produce energy
- -natural gas
- -petroleum
- -coal
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Fossil Fuel combustion products /// sources
- water, energy, carbon dioxide
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- electricity generation, transportation, industrial
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Carbon Cycle
exchange of carbon between earth's atmosphere, ocean, vegetation, and soil that occurs over days to thousands of years.
- carbon is not destroyed, but redistributed, on human timescales
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Photosynthesis
conversion by plants of inorganic carbon to organic carbon
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respiration:
conversion by life of organic carbon to inorganic carbon.
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Soil Formation
incorporation of litter(dead plant leaves and roots) to soils.
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Soil Respiration
escape of CO2 into the atmosphere through respiration/fermentation by plant roots, bacteria, fungi and soil animals.
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Ocean atmosphere gas exchange
- Exchange is driven by differences in co2
- -co2 dissolves in water
- -For every 10% increas in atmospheric co2 ,the surface ocean co2 will increase by 1%
- co2 exchange b/t surface ocean and atmosphere is fast(~1 year)
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solubility pump
physical and chemical processes that transport inorganic carbon from the ocean surface to interior
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Biological pump
physical and biological process that transport organic carbon from the surface to interior.
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