!!!!!!!!!!-------- Global warming- -------!!!!!!!!!!! Global warming is the observed century-scale rise in the average temperature of Earths climate system.Since 1971, 90% of the increased energy has been stored in the oceans, mostly in the 0 to 700m region.Despite the oceans dominant role in energy storage, the term global warming is also used to refer to increases in average temperature of the air and sea at Earths surface..Yet on current trends, continued burning of fossil fuels could see temperature increases of between 3.7C and 4.8C by the end of the century. Warming beyond 4C would likely result in “substantial species extinction, large risks to global and regional food security, impacts on normal human activities scientists were more than 90% certain that most of global warming was being caused by increasing concentrations of greenhouse gases produced by human activities. The largest driver of global warming is carbon dioxide (CO2) emissions from fossil fuel combustion, cement production, and land use changes such as deforestation.On Earth, naturally occurring amounts of greenhouse gases have a mean warming effect of about 33 °C (59 °F). Without the Earths atmosphere, the temperature across almost the entire surface of the Earth would be below freezing.The major greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect; carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%; and ozone (O3), which causes 3–7%.Clouds also affect the radiation balance through cloud forcings similar to greenhouse gases.Solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere.
Posted on: Sun, 02 Nov 2014 10:34:12 +0000
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