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On average, the energy from the sun received at the top of the Earth's atmosphere amounts to 175 petawatts (PW) (or 175 quadrillion watts), of which ~31% is reflected by clouds and from the surface. The rest (120 PW) is absorbed by the atmosphere, land, or ocean and ultimately emitted back to space as infrared radiation (ref 1 in reference article). This is for based on solar constant outside to the atmosphere. This is four order of magnitude more than used by humainty, and three orders of magnitude than harvested by photosynthesis by the biosphere. |