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Originally Posted by Lugnut  How is it that green house gas's have more effect on global temps than the 1.5X10^17 watts of solar energy that hit the earth every second? |
Greenhouse gases have a greater effect on earth's temperature than the sun, because the power emitted by the sun is essentially a constant (to be completely accurate, it varies by 1/10 of 1% on a reoccurring 11 year cycle). Consequently, the amount of power projected from the sun to the earth is also essentially constant: 1/2 the earth is always illuminated, 1/2 is always shadowed.
How much of the sun's power is actually absorbed on earth, and how much of the earth's heat is shed back into space - are largely governed by the composition of our atmosphere, which is much more variable than the sun's power. In that regard, more water vapor in the atmosphere means more of the sun's energy is reflected back into space (more cooling); more GHG mean less of the earth's heat is radiated back into space (less cooling). But the output of the sun remains essentially constant, and has little effect on the heat balance of the earth as a whole.
:edited for clarity