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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 
 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%) 
 Human: waste disposal sites (sewage, landfill, biomass burning) (28%) NB:...
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