Saturday, 5 April 2014

Green House Effect

What is the Greenhouse Effect?
The term greenhouse is used in conjunction with the phenomenon known as the greenhouse effect.
  • Energy from the sun drives the earth’s weather and climate, and heats the earth’s surface;
  • In turn, the earth radiates energy back into space;
  • Some atmospheric gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse;
  • These gases are therefore known as greenhouse gases;
  • The greenhouse effect is the rise in temperature on Earth as certain gases in the atmosphere trap energy.
Image source: Greenhouse Effect, Wikipedia(Link includes detailed explanation of the above image). Note, image above expresses energy exchanges in watts per square meter (W/m2)
Six main greenhouse gases are carbon dioxide (CO2), methane (CH4) (which is 20 times as potent a greenhouse gas as carbon dioxide) and nitrous oxide (N2O), plus three fluorinated industrial gases: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). Water vapor is also considered a greenhouse gas.
The Greenhouse effect is natural. What do we have to do with it?
Many of these greenhouse gases are actually life-enabling, for without them, heat would escape back into space and the Earth’s average temperature would be a lot colder.
However, if the greenhouse effect becomes stronger, then more heat gets trapped than needed, and the Earth might become less habitable for humans, plants and animals.
Carbon dioxide, though not the most potent of greenhouse gases, is the most significant one. Human activity has caused an imbalance in the natural cycle of the greenhouse effect and related processes. NASA’s Earth Observatory is worth quoting the effect human activity is having on the natural carbon cycle, for example:
In addition to the natural fluxes of carbon through the Earth system, anthropogenic (human) activities, particularly fossil fuel burning and deforestation, are also releasing carbon dioxide into the atmosphere.
When we mine coal and extract oil from the Earth’s crust, and then burn these fossil fuels for transportation, heating, cooking, electricity, and manufacturing, we are effectively moving carbon more rapidly into the atmosphere than is being removed naturally through the sedimentation of carbon, ultimately causing atmospheric carbon dioxide concentrations to increase.
Also, by clearing forests to support agriculture, we are transferring carbon from living biomass into the atmosphere (dry wood is about 50 percent carbon).
The result is that humans are adding ever-increasing amounts of extra carbon dioxide into the atmosphere. Because of this, atmospheric carbon dioxide concentrations are higher today than they have been over the last half-million years or longer.

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