chapter18

Source ru talk about keelings oxygen depletion 6

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Unformatted text preview: f carbon in fossil fuels (coal, oil, natural gas). (source: RU) talk about keeling’s oxygen depletion 
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 Figure 18.x Anthropogenic sources of the two greenhouse gases carbon dioxide and methane. Figure 18.x Anthropogenic sources of the two greenhouse gases carbon dioxide and methane. Greenhouse Gases o o o 
 H2O (most important greenhouse gas; huge variations due primarily to natural causes, i.e. climate and weather) CO2: amount of CO2 in atmosphere has increased by 39% from 280ppm in 1800 to 389ppm in 2010. Causes for change: Natural: temporarily also from volcanic activity, but the contribution in historical times has been insignificant Human: burning of biological mass and fossil fuels (80%) Human: removal of rainforest (though the contribution of this is relatively small) (17.3%) Human: cement production (smaller yet) (2.7%) NB: almost all of the current increase in CO2 is anthropogenic. CH4: has increased 150% from 0.7ppm in 1750 to 2ppm in 2000; more effective greenhouse gas than CO2 but less relevant due to slower current 7
 increase. This problem will become more prominent as the population increase requires more farming. Causes for change: Natural: wetlands (72%) Natural: termites (12.5%) Natural: ocean (6%) Natural: other (9.5%) Natural: recent global warming also releases methane in the tundra that has been "locked" in frozen ground (positive climate feedback) Natural: potential release of large amounts of gas hydrates from submarine icy lenses could happen, if current warming persists (at which point this actually happens is currently unknown) Natural: a natural gas seep offshore Santa Barbara releases significant amounts though most may be dissolved in water, unless it is transported very quickly to the sea surface Human: coal mining, natural gas, petroleum industry (27%) Human: rice paddies (16%) Human: cattle farming (enteric fermentation, animal wastes)(29%) 
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 Human: waste disposal sites (sewage, landfill, biomass burning) (28%) NB:...
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This document was uploaded on 11/21/2013.

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