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April 3rd

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McGill University
GEOG 205
Gail Chmura

April 3 , 2013  remember: we talked about astronomical variations in relation to climate  these will definitely be on the final*** o eccentricity has a period of 100 000 years  variance of solar output of 0.5 2 W/m o precession is the change in the earth’s axis, period of 19 000 to 26 000 year cycle o obliquity has a 41 000 year cycle  remember: the impacts of volcanic activity is episodic and irregular  volcanoes are not always erupting o they generally have a cooling effect since the particles of gas/dust block solar radiation from o relative amounts of C2  solid earth contains a huge quantity of carbon, far more than the atmosphere or oceans o as an important part of the global carbon cycle, some of this carbon in slowly released from the rocks in the form of carbon dioxide, through cents at volcanoes and hot springs o but the burning of fossil fuels and changes in land use result sin the emission into the atmosphere of approximately 30 billion ____ o amounts of CO2emitted by volcanoes quite small in relation to the amounts put out by humans  internal variability  the way in which the internal physics of the system can change the system o El Nino is an internal force o illustrates natural changes in circulation patterns o links to extreme weather events globally  many factors contribute to the warming of the earth, but many are not dramatic or rapid enough to explain the warming we see today  review: reasons for greenhouse gas effects on climate o gases absorb infrared radiation, heating atmosphere and slowing loss of radiation to space o strong correlation between earth temperature & concentration of gases in past o major greenhouse gases: carbon dioxide, ozone, water vapour, methane, nitrous oxide, CFCs  these aren’t normalized against 2O & are one molecule  primary sources for each gas: o CO2 burning of fossil fuels, land use (especially deforestation); can also remove CO 2hrough reforestation, improvement of soils, etc. o CH4 agricultural activities (cattle & sheep; emissions from rice patties), waste management o N2O  fertilizer use o CFCs  from industrial processes, refrigeration, variety of consumer products (aerosols) o black carbon is a solid particle/aerosol, not gas, that contributes to warming of atmosphere  reasons for increases in atmospheric CO2 concentrations o energy/electricity  creating energy for industries; burning of coal, natural gas & oil for electricity & heat = largest single course of global greenhouse gas emissions o industry  industries use energy to create products; fossil fuels burned on- site for energy; also includes emissions o land use  info from last class; deforestation, land clearing for agriculture, fires/decay of peat soils o agriculture management of soils, livestock, rice production, biomass burning o transportation  cars, jets, trains, ships, etc. o commercial/residential buildings  create their own energy o waste & wastewater  landfill methane, wastewater methane, nitrous oxide;  carbon dioxide (CO2) o 55% of present greenhouse gas climate forcing o temperature & carbon dioxide/methane concentration from Vostock ice core shows a rough approximation of historical temperatures vs. methane & carbon dioxide o CO2 & temperature closel
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